Autonomous vehicle lidar system using a waveguide array

ABSTRACT

An autonomous vehicle includes a LIDAR system that includes a waveguide array, a collimator configured to receive a plurality of beams from the waveguide array and output a plurality of collimated beams, and a scanner configured to adjust a direction of the plurality of collimated beams. The vehicle also includes one or more processors configured to determine a range to an object based on a return signal received from reflection or scattering of the plurality of collimated beams by the object and to control operation of at least one of a steering system or the braking system based on the range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/US2019/043488, filed Jul. 25, 2019, which claims the benefit of andpriority to U.S. Patent Application No. 62/717,200, filed Aug. 10, 2018.The entire disclosures of International Application No.PCT/US2019/043488 and U.S. Patent Application No. 62/717,200 are herebyincorporated by reference as if fully set forth herein.

BACKGROUND

Optical detection of range using lasers, often referenced by a mnemonic,LIDAR, for light detection and ranging, also sometimes called laserRADAR (radio-wave detection and ranging), is used for a variety ofapplications, from altimetry, to imaging, to collision avoidance. LIDARprovides finer scale range resolution with smaller beam sizes thanconventional microwave ranging systems, such as RADAR. Optical detectionof range can be accomplished with several different techniques,including direct ranging based on round trip travel time of an opticalpulse to an object, and chirped detection based on a frequencydifference between a transmitted chirped optical signal and a returnedsignal scattered from an object, and phase-encoded detection based on asequence of single frequency phase changes that are distinguishable fromnatural signals.

To achieve acceptable range accuracy and detection sensitivity, directlong range LIDAR systems use short pulse lasers with low pulserepetition rate and extremely high pulse peak power. The high pulsepower can lead to rapid degradation of optical components. Chirped andphase-encoded LIDAR systems use long optical pulses with relatively lowpeak optical power. In this configuration, the range accuracy increaseswith the chirp bandwidth or length and bandwidth of the phase codesrather than the pulse duration, and therefore excellent range accuracycan still be obtained.

Useful optical bandwidths have been achieved using wideband radiofrequency (RF) electrical signals to modulate an optical carrier. Recentadvances in LIDAR include using the same modulated optical carrier as areference signal that is combined with the returned signal at an opticaldetector to produce in the resulting electrical signal a relatively lowbeat frequency in the RF band that is proportional to the difference infrequencies or phases between the references and returned opticalsignals. This kind of beat frequency detection of frequency differencesat a detector is called heterodyne detection. It has several advantagesknown in the art, such as the advantage of using RF components of readyand inexpensive availability.

Recent work by current inventors, show a novel arrangement of opticalcomponents and coherent processing to detect Doppler shifts in returnedsignals that provide not only improved range but also relative signedspeed on a vector between the LIDAR system and each external object.These systems are called hi-res range-Doppler LIDAR herein. See forexample World Intellectual Property Organization (WIPO) publications WO2018/160240 and WO 2018/144853.

These improvements provide range, with or without target speed, in apencil thin laser beam of proper frequency or phase content. When suchbeams are swept over a scene, information about the location and speedof surrounding objects can be obtained. This information is expected tobe of value in control systems for autonomous vehicles, such asself-driving, or driver-assisted, automobiles.

SUMMARY

Conventional LIDAR systems include collimators that are used to producemultiple beams from one source beam. However, collimators inconventional LIDAR systems have notable drawbacks. The inventorsrecognized that these collimators typically satisfy one or more designparameters of conventional LIDAR systems but frequently fail to satisfyother design parameters of the system. For example, large beamcollimators can produce a desired beam size but cannot be packed closeenough to achieve a desired angular spacing. In another example, arraycollimators can produce beams that are sufficiently close together butdo not provide a large enough beam size for the LIDAR system. Here isdescribed a collimator which overcomes these noted drawbacks.Additionally, this collimator is used in various scanning apparatusesand methods to achieve an improved scanning LIDAR. For example, ascanning apparatus employs a polygon scanner that rotates at a fixedspeed in conjunction with the collimator to achieve a more efficientscanning than conventional scanning techniques.

The sampling and processing that provides range accuracy and targetspeed accuracy involve integration of one or more laser signals ofvarious durations, in a time interval called integration time. To covera scene in a timely way involves repeating a measurement of sufficientaccuracy (involving one or more signals often over one to tens ofmicroseconds) often enough to sample a variety of angles (often on theorder of thousands) around the autonomous vehicle to understand theenvironment around the vehicle before the vehicle advances too far intothe space ahead of the vehicle (a distance on the order of one to tensof meters, often covered in a particular time on the order of one to afew seconds). The number of different angles that can be covered in theparticular time (often called the cycle or sampling time) depends on thesampling rate. The current inventors have recognized that a tradeoff canbe made between integration time for range and speed accuracy, samplingrate, and pattern of sampling different angles, with one or more LIDARbeams, to effectively determine the environment in the vicinity of anautonomous vehicle as the vehicle moves through that environment.

In a first set of embodiments, an assembly apparatus for a LIDAR systemincludes a waveguide array arranged in a first plane. The waveguidearray is configured to generate a plurality of beams where each beam istransmitted from a respective waveguide in the array. The apparatus alsoincludes a collimator configured to shape the plurality of beams into afan of collimated beams having an angular spread in the first plane.Additionally, the apparatus includes a polygon scanner configured toadjust a direction of the fan in a second plane that is different thanthe first plane.

In a second set of embodiments, a system is provided that includes theassembly above and further includes a processor, a memory and a sequenceof instructions that are configured to cause the system to receive afirst angle and a second angle in the second plane that define an anglerange of a scan pattern of the fan and to adjust the direction of thefan in the second plane using the polygon scanner from the first angleto the second angle; and to receive a plurality of return beamsencompassing the angular spread of a target at a range.

In a third set of embodiments, a method is provided that includesgenerating a plurality of beams with a waveguide array of a LIDAR systemarranged in a first plane, where each beam is transmitted from arespective waveguide in the array. The method further includes shapingthe plurality of beams with a collimator into a fan of collimated beamshaving an angular spread in the first plane. The method further includesreceiving, on a processor, a first angle and a second angle in a secondplane different than the first plane, where the first angle and thesecond angle defines an angle range of a scan pattern of the fan in thesecond plane. The method further includes adjusting a direction of thefan in the second plane with a polygon scanner from the first angle tothe second angle to form the scan pattern. The method further includesreceiving, at the waveguide in the array, a return beam from a targetlocated at a range.

In a fourth set of embodiments, a method is provided that includesgenerating a plurality of beams with a waveguide array of a LIDAR systemarranged in a first plane, where each beam is transmitted from arespective waveguide in the array. The method further includes shapingthe plurality of beams with a collimator into a fan of collimated beamshaving an angular spread in the first plane. The method further includesreceiving, on a processor, a first angle and a second angle in a secondplane different than the first plane, where the first angle and thesecond angle defines an angle range of a scan pattern of the fan in thesecond plane. The method further includes adjusting, with a scanner, afirst component of a gross trajectory of the fan in two dimensionalspace defined by the first and second plane, where the first componentis a first incremental angle in the first plane. The method furtherincludes adjusting, with the scanner, a second component of the grosstrajectory of the fan, where the second component is a secondincremental angle in the second plane. The method further includesswitching between each waveguide in the array for each component of thegross trajectory, to emit a transmit beam from the waveguide and receivea return beam at the waveguide.

Still other aspects, features, and advantages are readily apparent fromthe following detailed description, simply by illustrating a number ofparticular embodiments and implementations, including the best modecontemplated for carrying out the invention. Other embodiments are alsocapable of other and different features and advantages, and theirseveral details can be modified in various obvious respects, all withoutdeparting from the spirit and scope of the invention. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated by way of example, and not by way oflimitation, in the figures of the accompanying drawings in which likereference numerals refer to similar elements and in which:

FIG. 1A is a schematic graph that illustrates the example transmittedsignal of a series of binary digits along with returned optical signalsfor measurement of range, according to an embodiment;

FIG. 1B is a schematic graph that illustrates an example spectrum of thereference signal and an example spectrum of a Doppler shifted returnsignal, according to an embodiment;

FIG. 1C is a schematic graph that illustrates an example cross-spectrumof phase components of a Doppler shifted return signal, according to anembodiment;

FIG. 1D is a set of graphs that illustrates an example optical chirpmeasurement of range, according to an embodiment;

FIG. 1E is a graph using a symmetric LO signal, and shows the returnsignal in this frequency time plot as a dashed line when there is noDoppler shift, according to an embodiment;

FIG. 1F is a graph similar to FIG. 1E, using a symmetric LO signal, andshows the return signal in this frequency time plot as a dashed linewhen there is a non-zero Doppler shift, according to an embodiment;

FIG. 2A is a block diagram that illustrates example components of ahigh-resolution (hi res) LIDAR system, according to an embodiment;

FIG. 2B is a block diagram that illustrates a saw tooth scan pattern fora hi-res Doppler system, used in some embodiments;

FIG. 2C is an image that illustrates an example speed point cloudproduced by a hi-res Doppler LIDAR system, according to an embodiment;

FIG. 2D is a block diagram that illustrates example components of a highresolution (hi res) LIDAR system, according to an embodiment;

FIG. 2E is a block diagram that illustrates example of a cross-sectionalside view of a collimator used in a high-resolution LIDAR system with awaveguide array to form a collimated fan beam, according to anembodiment;

FIG. 2F is a block diagram that illustrates example of a ray diagram ofthe collimator of FIG. 2E shaping one beam in the collimated fan beam,according to an embodiment;

FIG. 2G is a block diagram that illustrates example components to scan adirection of the collimated fan beam of FIG. 2E over a range of angles,according to an embodiment;

FIG. 2H is a block diagram that illustrates a top view of the componentsof FIG. 2G, according to an embodiment;

FIG. 2I is a block diagram that illustrates example optical switchesused in the system of FIG. 2G to switch between one or more waveguidesof the array, according to an embodiment;

FIG. 3A is a block diagram that illustrates an example system thatincludes at least one hi-res LIDAR system mounted on a vehicle,according to an embodiment;

FIG. 3B is a block diagram that illustrates an example system thatincludes at least one hi-res LIDAR system mounted on a vehicle,according to an embodiment;

FIG. 4A is an image that illustrates an example of multiple interleaveswipes of the collimated fan beam using the system of FIG. 2G, accordingto an embodiment;

FIG. 4B is an image that illustrates an example of multiple offsetswipes of the collimated fan beam using the system of FIG. 2G, accordingto an embodiment;

FIG. 4C is an image that illustrates an example of one swipe of thecollimated fan beam using the system of FIG. 2G where the waveguides inthe array are irregularly spaced, according to an embodiment;

FIG. 4D is a graph that illustrates a gross trajectory of a collimatedfan beam scanned with a mechanical scanner, according to an embodiment;

FIG. 4E is a graph that illustrates the gross trajectory of FIG. 4D andreturn beam data received from the waveguide array based on switchingbetween waveguides, according to an embodiment;

FIG. 4F is a graph that illustrates an example of a time axis indicatingthe switch time values between adjacent waveguides to generate thereturn beam data in FIG. 4E, according to an embodiment;

FIG. 4G is a graph that illustrates an example of scan direction versustime for the scanners in the system of FIG. 2G, according to anembodiment;

FIG. 5A is an image that illustrates an example of beam walkoff forvarious target ranges and scan speeds in the system of FIG. 2D,according to an embodiment;

FIG. 5B is a graph that illustrates an example of coupling efficiencyversus target range for various scan rates in the system of FIG. 2D,according to an embodiment;

FIG. 6A is a flow chart that illustrates an example method for operatinga scanner of a LIDAR system, according to an embodiment;

FIG. 6B is a flow chart that illustrates an example method for operatinga scanner of a LIDAR system, according to an embodiment;

FIG. 6C is a flow chart that illustrates an example method for operatinga scanner of a LIDAR system, according to an embodiment;

FIG. 7 is a block diagram that illustrates a computer system upon whichan embodiment of the invention may be implemented; and

FIG. 8 illustrates a chip set upon which an embodiment of the inventionmay be implemented.

DETAILED DESCRIPTION

A method and apparatus and system and computer-readable medium aredescribed for scanning a fan of collimated beams of a LIDAR system. Inthe following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however, toone skilled in the art that the present invention may be practicedwithout these specific details. In other instances, well-knownstructures and devices are shown in block diagram form in order to avoidunnecessarily obscuring the present invention.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope are approximations, the numerical values set forth inspecific non-limiting examples are reported as precisely as possible.Any numerical value, however, inherently contains certain errorsnecessarily resulting from the standard deviation found in theirrespective testing measurements at the time of this writing.Furthermore, unless otherwise clear from the context, a numerical valuepresented herein has an implied precision given by the least significantdigit. Thus a value 1.1 implies a value from 1.05 to 1.15. The term“about” is used to indicate a broader range centered on the given value,and unless otherwise clear from the context implies a broader rangearound the least significant digit, such as “about 1.1” implies a rangefrom 1.0 to 1.2. If the least significant digit is unclear, then theterm “about” implies a factor of two, e.g., “about X” implies a value inthe range from 0.5× to 2×, for example, about 100 implies a value in arange from 50 to 200. Moreover, all ranges disclosed herein are to beunderstood to encompass any and all sub-ranges subsumed therein. Forexample, a range of “less than 10” for a positive only parameter caninclude any and all sub-ranges between (and including) the minimum valueof zero and the maximum value of 10, that is, any and all sub-rangeshaving a minimum value of equal to or greater than zero and a maximumvalue of equal to or less than 10, e.g., 1 to 4.

Some embodiments of the invention are described below in the context ofa LIDAR system that generates a collimated fan of beams that can bescanned across a scan pattern defined by a first angle and a secondangle. In other embodiments, the invention is described in the contextof a single front mounted hi-res Doppler LIDAR system on a personalautomobile; but, embodiments are not limited to these contexts. In otherembodiments, one or multiple systems of the same type or otherhigh-resolution LIDAR, with or without Doppler components, withoverlapping or non-overlapping fields of view or one or more suchsystems mounted on smaller or larger land, sea, air or space vehicles,piloted or autonomous, are employed. In still other embodiments, theinvention is described in the context of static LIDAR, such as on aLIDAR system mounted on a tripod or positioned in a surveillance tower.

1. PHASE-ENCODED DETECTION OVERVIEW

Using an optical phase-encoded signal for measurement of range, thetransmitted signal is in phase with a carrier (phase=0) for part of thetransmitted signal and then changes by one or more phase changesrepresented by the symbol Δϕ (so phase=0, Δϕ, 2Δϕ . . . ) for short timeintervals, switching back and forth between the two or more phase valuesrepeatedly over the transmitted signal. The shortest interval ofconstant phase is a parameter of the encoding called pulse duration τand is typically the duration of several periods of the lowest frequencyin the band. The reciprocal, 1/τ, is baud rate, where each baudindicates a symbol. The number N of such constant phase pulses duringthe time of the transmitted signal is the number N of symbols andrepresents the length of the encoding. In binary encoding, there are twophase values and the phase of the shortest interval can be considered a0 for one value and a 1 for the other, thus the symbol is one bit, andthe baud rate is also called the bit rate. In multiphase encoding, thereare multiple phase values. For example, 4 phase values such as Δϕ* {0,1, 2 and 3}, which, for Δϕ=π/2 (90 degrees), equals {0, π/2, π and3π/2}, respectively; and, thus 4 phase values can represent 0, 1, 2, 3,respectively. In this example, each symbol is two bits and the bit rateis twice the baud rate.

Phase-shift keying (PSK) refers to a digital modulation scheme thatconveys data by changing (modulating) the phase of a reference signal(the carrier wave). The modulation is impressed by varying the sine andcosine inputs at a precise time. At radio frequencies (RF), PSK iswidely used for wireless local area networks (LANs), RF identification(RFID) and Bluetooth communication. Alternatively, instead of operatingwith respect to a constant reference wave, the transmission can operatewith respect to itself. Changes in phase of a single transmittedwaveform can be considered the symbol. In this system, the demodulatordetermines the changes in the phase of the received signal rather thanthe phase (relative to a reference wave) itself. Since this schemedepends on the difference between successive phases, it is termeddifferential phase-shift keying (DPSK). DPSK can be significantlysimpler to implement in communications applications than ordinary PSK,since there is no need for the demodulator to have a copy of thereference signal to determine the exact phase of the received signal(thus, it is a non-coherent scheme).

For optical ranging applications, since the transmitter and receiver arein the same device, coherent PSK can be used. The carrier frequency isan optical frequency fc and a RF f₀ is modulated onto the opticalcarrier. The number N and duration τ of symbols are selected to achievethe desired range accuracy and resolution. The pattern of symbols isselected to be distinguishable from other sources of coded signals andnoise. Thus, a strong correlation between the transmitted and returnedsignal is a strong indication of a reflected or backscattered signal.The transmitted signal is made up of one or more blocks of symbols,where each block is sufficiently long to provide strong correlation witha reflected or backscattered return even in the presence of noise. Inthe following discussion, it is assumed that the transmitted signal ismade up of M blocks of N symbols per block, where M and N arenon-negative integers.

FIG. 1A is a schematic graph 120 that illustrates the exampletransmitted signal as a series of binary digits along with returnedoptical signals for measurement of range, according to an embodiment.The horizontal axis 122 indicates time in arbitrary units after a starttime at zero. The vertical axis 124 a indicates amplitude of an opticaltransmitted signal at frequency fc+f₀ in arbitrary units relative tozero. The vertical axis 124 b indicates amplitude of an optical returnedsignal at frequency fc+f₀ in arbitrary units relative to zero; and, isoffset from axis 124 a to separate traces. Trace 125 represents atransmitted signal of M*N binary symbols, with phase changes as shown inFIG. 1A to produce a code starting with 00011010 and continuing asindicated by ellipsis. Trace 126 represents an idealized (noiseless)return signal that is scattered from an object that is not moving (andthus the return is not Doppler shifted). The amplitude is reduced, butthe code 00011010 is recognizable. Trace 127 represents an idealized(noiseless) return signal that is scattered from an object that ismoving and is therefore Doppler shifted. The return is not at the properoptical frequency fc+f₀ and is not well detected in the expectedfrequency band, so the amplitude is diminished.

The observed frequency f′ of the return differs from the correctfrequency f=fc+f₀ of the return by the Doppler effect given by Equation1.

$\begin{matrix}{f^{\prime} = {\frac{( {c + v_{o}} )}{( {c + v_{s}} )}f}} & (1)\end{matrix}$

Where c is the speed of light in the medium, v_(o) is the velocity ofthe observer and v_(s) is the velocity of the source along the vectorconnecting source to receiver. Note that the two frequencies are thesame if the observer and source are moving at the same speed in the samedirection on the vector between the two. The difference between the twofrequencies, Δf=f′−f, is the Doppler shift, Δf_(D), which causesproblems for the range measurement, and is given by Equation 2.

$\begin{matrix}{{\Delta \; f_{D}} = {\lbrack {\frac{( {c + v_{o}} )}{( {c + v_{s}} )} - 1} \rbrack f}} & (2)\end{matrix}$

Note that the magnitude of the error increases with the frequency f ofthe signal. Note also that for a stationary LIDAR system (v_(o)=0), foran object moving at 10 meters a second (v_(s)=10), and visible light offrequency about 500 THz, then the size of the Doppler shift is on theorder of 16 megahertz (MHz, 1 MHz=10⁶ hertz, Hz, 1 Hz=1 cycle persecond). In various embodiments described below, the Doppler shift isdetected and used to process the data for the calculation of range.

In phase coded ranging, the arrival of the phase coded return isdetected in the return signal by cross correlating the transmittedsignal or other reference signal with the returned signal, implementedpractically by cross correlating the code for a RF signal with aelectrical signal from an optical detector using heterodyne detectionand thus down-mixing back to the RF band. Cross correlation for any onelag is computed by convolving the two traces, i.e., multiplyingcorresponding values in the two traces and summing over all points inthe trace, and then repeating for each time lag. Alternatively, thecross correlation can be accomplished by a multiplication of the Fouriertransforms of each of the two traces followed by an inverse Fouriertransform. Efficient hardware and software implementations for a FastFourier transform (FFT) are widely available for both forward andinverse Fourier transforms.

Note that the cross-correlation computation is typically done withanalog or digital electrical signals after the amplitude and phase ofthe return is detected at an optical detector. To move the signal at theoptical detector to a RF frequency range that can be digitized easily,the optical return signal is optically mixed with the reference signalbefore impinging on the detector. A copy of the phase-encodedtransmitted optical signal can be used as the reference signal, but itis also possible, and often preferable, to use the continuous wavecarrier frequency optical signal output by the laser as the referencesignal and capture both the amplitude and phase of the electrical signaloutput by the detector.

For an idealized (noiseless) return signal that is reflected from anobject that is not moving (and thus the return is not Doppler shifted),a peak occurs at a time Δt after the start of the transmitted signal.This indicates that the returned signal includes a version of thetransmitted phase code beginning at the time Δt. The range R to thereflecting (or backscattering) object is computed from the two waytravel time delay based on the speed of light c in the medium, as givenby Equation 3.

R=c*Δt/2  (3)

For an idealized (noiseless) return signal that is scattered from anobject that is moving (and thus the return is Doppler shifted), thereturn signal does not include the phase encoding in the properfrequency bin, the correlation stays low for all time lags, and a peakis not as readily detected, and is often undetectable in the presence ofnoise. Thus Δt is not as readily determined; and, range R is not asreadily produced.

According to various embodiments of the inventor's previous work, theDoppler shift is determined in the electrical processing of the returnedsignal; and the Doppler shift is used to correct the cross-correlationcalculation. Thus, a peak is more readily found and range can be morereadily determined. FIG. 1B is a schematic graph 140 that illustrates anexample spectrum of the transmitted signal and an example spectrum of aDoppler shifted complex return signal, according to an embodiment. Thehorizontal axis 142 indicates RF frequency offset from an opticalcarrier fc in arbitrary units. The vertical axis 144 a indicatesamplitude of a particular narrow frequency bin, also called spectraldensity, in arbitrary units relative to zero. The vertical axis 144 bindicates spectral density in arbitrary units relative to zero; and, isoffset from axis 144 a to separate traces. Trace 145 represents atransmitted signal; and, a peak occurs at the proper RF f₀. Trace 146represents an idealized (noiseless) complex return signal that isbackscattered from an object that is moving toward the LIDAR system andis therefore Doppler shifted to a higher frequency (called blueshifted). The return does not have a peak at the proper RF, f₀; but,instead, is blue shifted by Δf_(D) to a shifted frequency f_(S). Inpractice, a complex return representing both in-phase and quadrature(I/Q) components of the return is used to determine the peak at +Δf_(D),thus the direction of the Doppler shift, and the direction of motion ofthe target on the vector between the sensor and the object, is apparentfrom a single return.

In some Doppler compensation embodiments, rather than finding Δf_(D) bytaking the spectrum of both transmitted and returned signals andsearching for peaks in each, then subtracting the frequencies ofcorresponding peaks, as illustrated in FIG. 1B, it is more efficient totake the cross spectrum of the in-phase and quadrature component of thedown-mixed returned signal in the RF band. FIG. 1C is a schematic graph150 that illustrates an example cross-spectrum, according to anembodiment. The horizontal axis 152 indicates frequency shift inarbitrary units relative to the reference spectrum; and, the verticalaxis 154 indicates amplitude of the cross spectrum in arbitrary unitsrelative to zero. Trace 155 represents a cross spectrum with anidealized (noiseless) return signal generated by one object movingtoward the LIDAR system (blue shift of Δf_(D1)=Δf_(D) in FIG. 1B) and asecond object moving away from the LIDAR system (red shift of Δf_(D2)).A peak occurs when one of the components is blue shifted Δf_(D1); and,another peak occurs when one of the components is red shifted Δf_(D2).Thus the Doppler shifts are determined. These shifts can be used todetermine a signed velocity of approach of objects in the vicinity ofthe LIDAR, as can be critical for collision avoidance applications.However, if I/Q processing is not done, peaks appear at both +/−Δf_(D1)and both +/−Δf_(D2), so there is ambiguity on the sign of the Dopplershift and thus the direction of movement.

As described in more detail in inventor's previous work the Dopplershift(s) detected in the cross spectrum are used to correct the crosscorrelation so that the peak 135 is apparent in the Doppler compensatedDoppler shifted return at lag Δt, and range R can be determined. In someembodiments simultaneous I/Q processing is performed as described inmore detail in World Intellectual Property Organization publication WO2018/144853 entitled “Method and system for Doppler detection andDoppler correction of optical phase-encoded range detection”, the entirecontents of which are hereby incorporated by reference as if fully setforth herein. In other embodiments, serial I/Q processing is used todetermine the sign of the Doppler return as described in more detail inWorld Intellectual Property Organization publication WO 2019/014177entitled “Method and System for Time Separated Quadrature Detection ofDoppler Effects in Optical Range Measurements”, the entire contents ofwhich are hereby incorporated by reference as if fully set forth herein.In other embodiments, other means are used to determine the Dopplercorrection; and, in various embodiments, any method known in the art toperform Doppler correction is used. In some embodiments, errors due toDoppler shifting are tolerated or ignored; and, no Doppler correction isapplied to the range measurements.

2. CHIRPED DETECTION OVERVIEW

FIG. 1D is a set of graphs that illustrates an example optical chirpmeasurement of range, according to an embodiment. The horizontal axis102 is the same for all four graphs and indicates time in arbitraryunits, on the order of milliseconds (ms, 1 ms=10⁻³ seconds). Graph 100indicates the power of a beam of light used as a transmitted opticalsignal. The vertical axis 104 in graph 100 indicates power of thetransmitted signal in arbitrary units. Trace 106 indicates that thepower is on for a limited pulse duration, τ starting at time 0. Graph110 indicates the frequency of the transmitted signal. The vertical axis114 indicates the frequency transmitted in arbitrary units. The trace116 indicates that the frequency of the pulse increases from f₁ to f₂over the duration τ of the pulse, and thus has a bandwidth B=f₂−f₁. Thefrequency rate of change is (f₂−f₁)/τ.

The returned signal is depicted in graph 160 which has a horizontal axis102 that indicates time and a vertical axis 114 that indicates frequencyas in graph 110. The chirp 116 of graph 110 is also plotted as a dottedline on graph 160. A first returned signal is given by trace 166 a,which is just the transmitted reference signal diminished in intensity(not shown) and delayed by Δt. When the returned signal is received froman external object after covering a distance of 2R, where R is the rangeto the target, the returned signal start at the delayed time Δt is givenby 2R/c, where c is the speed of light in the medium (approximately3×10⁸ meters per second, m/s), related according to Equation 3,described above. Over this time, the frequency has changed by an amountthat depends on the range, called f_(R), and given by the frequency rateof change multiplied by the delay time. This is given by Equation 4a.

f _(R)=(f ₂ −f ₁)/τ*2R/c=2BR/cτ  (4a)

The value of f_(R) is measured by the frequency difference between thetransmitted signal 116 and returned signal 166 a in a time domain mixingoperation referred to as de-chirping. So the range R is given byEquation 4b.

R=f _(R) cτ/2B  (4b)

Of course, if the returned signal arrives after the pulse is completelytransmitted, that is, if 2R/c is greater than τ, then Equations 4a and4b are not valid. In this case, the reference signal is delayed a knownor fixed amount to ensure the returned signal overlaps the referencesignal. The fixed or known delay time of the reference signal ismultiplied by the speed of light, c, to give an additional range that isadded to range computed from Equation 4b. While the absolute range maybe off due to uncertainty of the speed of light in the medium, this is anear-constant error and the relative ranges based on the frequencydifference are still very precise.

In some circumstances, a spot (pencil beam cross section) illuminated bythe transmitted light beam encounters two or more different scatterersat different ranges, such as a front and a back of a semitransparentobject, or the closer and farther portions of an object at varyingdistances from the LIDAR, or two separate objects within the illuminatedspot. In such circumstances, a second diminished intensity anddifferently delayed signal will also be received, indicated on graph 160by trace 166 b. This will have a different measured value of f_(R) thatgives a different range using Equation 4b. In some circumstances,multiple additional returned signals are received.

Graph 170 depicts the difference frequency f_(R) between a firstreturned signal 166 a and the reference chirp 116. The horizontal axis102 indicates time as in all the other aligned graphs in FIG. 1D, andthe vertical axis 164 indicates frequency difference on a much-expandedscale. Trace 176 depicts the constant frequency f_(R) measured inresponse to the transmitted chirp, which indicates a particular range asgiven by Equation 4b. The second returned signal 166 b, if present,would give rise to a different, larger value of f_(R) (not shown) duringde-chirping; and, as a consequence yield a larger range using Equation4b.

A common method for de-chirping is to direct both the reference opticalsignal and the returned optical signal to the same optical detector. Theelectrical output of the detector is dominated by a beat frequency thatis equal to, or otherwise depends on, the difference in the frequenciesof the two signals converging on the detector. A Fourier transform ofthis electrical output signal will yield a peak at the beat frequency.This beat frequency is in the radio frequency (RF) range of Megahertz(MHz, 1 MHz=10⁶ Hertz=10⁶ cycles per second) rather than in the opticalfrequency range of Terahertz (THz, 1 THz=10¹² Hertz). Such signals arereadily processed by common and inexpensive RF components, such as aFast Fourier Transform (FFT) algorithm running on a microprocessor or aspecially built FFT or other digital signal processing (DSP) integratedcircuit. In other embodiments, the return signal is mixed with acontinuous wave (CW) tone acting as the local oscillator (versus a chirpas the local oscillator). This leads to the detected signal which itselfis a chirp (or whatever waveform was transmitted). In this case thedetected signal would undergo matched filtering in the digital domain asdescribed in Kachelmyer 1990, the entire contents of which are herebyincorporated by reference as if fully set forth herein, except forterminology inconsistent with that used herein. The disadvantage is thatthe digitizer bandwidth requirement is generally higher. The positiveaspects of coherent detection are otherwise retained.

In some embodiments, the LIDAR system is changed to produce simultaneousup and down chirps. This approach eliminates variability introduced byobject speed differences, or LIDAR position changes relative to theobject which actually does change the range, or transient scatterers inthe beam, among others, or some combination. The approach thenguarantees that the Doppler shifts and ranges measured on the up anddown chirps are indeed identical and can be most usefully combined. TheDoppler scheme guarantees parallel capture of asymmetrically shiftedreturn pairs in frequency space for a high probability of correctcompensation.

FIG. 1E is a graph using a symmetric LO signal; and, shows the returnsignal in this frequency time plot as a dashed line when there is noDoppler shift, according to an embodiment. The horizontal axis indicatestime in example units of 10⁻⁵ seconds (tens of microseconds). Thevertical axis indicates frequency of the optical transmitted signalrelative to the carrier frequency f_(c) or reference signal in exampleunits of gigaHertz (GHz, 1 GHz=10⁹ Hertz). During a pulse duration, alight beam comprising two optical frequencies at any time is generated.One frequency increases from f₁ to f₂ (e.g., 1 to 2 GHz above theoptical carrier) while the other frequency simultaneous decreases fromf₄ to f₃ (e.g., 1 to 2 GHz below the optical carrier) The two frequencybands e.g., band 1 from f₁ to f₂, and band 2 from f₃ to f₄) do notoverlap so that both transmitted and return signals can be opticallyseparated by a high pass or a low pass filter, or some combination, withpass bands starting at pass frequency f_(p). For examplef₁<f₂<f_(p)<f₃<f₄. Though, in the illustrated embodiment, the higherfrequencies provide the up chirp and the lower frequencies provide thedown chirp, in other embodiments, the higher frequencies produce thedown chirp and the lower frequencies produce the up chirp.

In some embodiments, two different laser sources are used to produce thetwo different optical frequencies in each beam at each time. However, insome embodiments, a single optical carrier is modulated by a single RFchirp to produce symmetrical sidebands that serve as the simultaneous upand down chirps. In some of these embodiments, a double sidebandMach-Zehnder intensity modulator is used that, in general, does notleave much energy in the carrier frequency; instead, almost all of theenergy goes into the sidebands.

As a result of sideband symmetry, the bandwidth of the two opticalchirps will be the same if the same order sideband is used. In otherembodiments, other sidebands are used, e.g., two second order sidebandare used, or a first order sideband and a non-overlapping secondsideband is used, or some other combination.

As described in World Intellectual Property Organization publication WO2018/160240, entitled “Method and System for Doppler Detection andDoppler Correction of Optical Chirped Range Detection,” the entirecontents of which are hereby incorporated by reference as if fully setforth herein, when selecting the transmit (TX) and local oscillator (LO)chirp waveforms, it is advantageous to ensure that the frequency shiftedbands of the system take maximum advantage of available digitizerbandwidth. In general, this is accomplished by shifting either the upchirp or the down chirp to have a range frequency beat close to zero.

FIG. 1F is a graph similar to FIG. 1E, using a symmetric LO signal, andshows the return signal in this frequency time plot as a dashed linewhen there is a non-zero Doppler shift. For example, if the blue shiftcausing range effects is f_(B), then the beat frequency of the up chirpwill be increased by the offset and occur at f_(B)+Δf_(S) and the beatfrequency of the down chirp will be decreased by the offset tof_(B)−Δf_(S). Thus, the up chirps will be in a higher frequency bandthan the down chirps, thereby separating them. If Δf_(S) is greater thanany expected Doppler effect, there will be no ambiguity in the rangesassociated with up chirps and down chirps. The measured beats can thenbe corrected with the correctly signed value of the known Δf_(S) to getthe proper up-chirp and down-chirp ranges. In the case of a chirpedwaveform, the time separated I/Q processing (aka time domainmultiplexing) can be used to overcome hardware requirements of otherapproaches as described above. In that case, an AOM is used to break therange-Doppler ambiguity for real valued signals. In some embodiments, ascoring system is used to pair the up and down chirp returns asdescribed in more detail in the above cited publication. In otherembodiments, I/Q processing is used to determine the sign of the Dopplerchirp as described in more detail above.

3. OPTICAL DETECTION HARDWARE OVERVIEW

In order to depict how to use hi-res range-Doppler detection systems,some generic hardware approaches are described. FIG. 2A is a blockdiagram that illustrates example components of a high resolution rangeLIDAR system 200, according to an embodiment. Optical signals areindicated by arrows. Electronic wired or wireless connections areindicated by segmented lines without arrowheads. A laser source 212emits a carrier wave 201 that is phase or frequency modulated inmodulator 282 a, before or after splitter 216, to produce a phase codedor chirped optical signal 203 that has a duration D. A splitter 216splits the modulated (or, as shown, the unmodulated) optical signal foruse in a reference path 220. A target beam 205, also called transmittedsignal herein, with most of the energy of the beam 201 is produced. Amodulated or unmodulated reference beam 207 a with a much smaller amountof energy that is nonetheless enough to produce good mixing with thereturned light 291 scattered from an object (not shown) is alsoproduced. In the illustrated embodiment, the reference beam 207 a isseparately modulated in modulator 282 b. The reference beam 207 a passesthrough reference path 220 and is directed to one or more detectors asreference beam 207 b. In some embodiments, the reference path 220introduces a known delay sufficient for reference beam 207 b to arriveat the detector array 230 with the scattered light from an objectoutside the LIDAR within a spread of ranges of interest. In someembodiments, the reference beam 207 b is called the local oscillator(LO) signal referring to older approaches that produced the referencebeam 207 b locally from a separate oscillator. In various embodiments,from less to more flexible approaches, the reference is caused to arrivewith the scattered or reflected field by: 1) putting a mirror in thescene to reflect a portion of the transmit beam back at the detectorarray so that path lengths are well matched; 2) using a fiber delay toclosely match the path length and broadcast the reference beam withoptics near the detector array, as suggested in FIG. 2A, with or withouta path length adjustment to compensate for the phase or frequencydifference observed or expected for a particular range; or, 3) using afrequency shifting device (acousto-optic modulator) or time delay of alocal oscillator waveform modulation (e.g., in modulator 282 b) toproduce a separate modulation to compensate for path length mismatch; orsome combination. In some embodiments, the object is close enough andthe transmitted duration long enough that the returns sufficientlyoverlap the reference signal without a delay.

The transmitted signal is then transmitted to illuminate an area ofinterest, often through some scanning optics 218. The detector array isa single paired or unpaired detector or a 1 dimensional (1D) or 2dimensional (2D) array of paired or unpaired detectors arranged in aplane roughly perpendicular to returned beams 291 from the object. Thereference beam 207 b and returned beam 291 are combined in zero or moreoptical mixers 284 to produce an optical signal of characteristics to beproperly detected. The frequency, phase or amplitude of the interferencepattern, or some combination, is recorded by acquisition system 240 foreach detector at multiple times during the signal duration D. The numberof temporal samples processed per signal duration or integration timeaffects the down-range extent. The number or integration time is often apractical consideration chosen based on number of symbols per signal,signal repetition rate and available camera frame rate. The frame rateis the sampling bandwidth, often called “digitizer frequency.” The onlyfundamental limitations of range extent are the coherence length of thelaser and the length of the chirp or unique phase code before it repeats(for unambiguous ranging). This is enabled because any digital record ofthe returned heterodyne signal or bits could be compared or crosscorrelated with any portion of transmitted bits from the priortransmission history.

The acquired data is made available to a processing system 250, such asa computer system described below with reference to FIG. 7, or a chipset described below with reference to FIG. 8. A scanner control module270 provides scanning signals to drive the scanning optics 218 and/orthe source 212 and/or the first and second scanner 241, 244 (FIG. 2G)and/or the optical switches 247 (FIG. 2J), according to one or more ofthe embodiments described below. In one embodiment, the scanner controlmodule 270 includes instructions to perform one or more steps of themethod 600 described below with reference to the flowchart of FIG. 6Aand/or method 630 described below with reference to the flowchart ofFIG. 6B and/or method 650 described below with reference to theflowchart of FIG. 6C. A signed Doppler compensation module (not shown)in processing system 250 determines the sign and size of the Dopplershift and the corrected range based thereon along with any othercorrections. The processing system 250 also includes a modulation signalmodule (not shown) to send one or more electrical signals that drivemodulators 282 a, 282 b. In some embodiments, the processing system alsoincludes a vehicle control module 272 to control a vehicle on which thesystem 200 is installed.

Any known apparatus or system may be used to implement the laser source212, modulators 282 a, 282 b, beam splitter 216, reference path 220,optical mixers 284, detector array 230, scanning optics 218, oracquisition system 240. Optical coupling to flood or focus on a targetor focus past the pupil plane are not depicted. As used herein, anoptical coupler is any component that affects the propagation of lightwithin spatial coordinates to direct light from one component to anothercomponent, such as a vacuum, air, glass, crystal, mirror, lens, opticalcirculator, beam splitter, phase plate, polarizer, optical fiber,optical mixer, among others, alone or in some combination.

FIG. 2A also illustrates example components for a simultaneous up anddown chirp LIDAR system according to one embodiment. In this embodiment,the modulator 282 a is a frequency shifter added to the optical path ofthe transmitted beam 205. In other embodiments, the frequency shifter isadded instead to the optical path of the returned beam 291 or to thereference path 220. In general, the frequency shifting element is addedas modulator 282 b on the local oscillator (LO, also called thereference path) side or on the transmit side (before the opticalamplifier) as the device used as the modulator (e.g., an acousto-opticmodulator, AOM) has some loss associated and it is disadvantageous toput lossy components on the receive side or after the optical amplifier.The purpose of the optical shifter is to shift the frequency of thetransmitted signal (or return signal) relative to the frequency of thereference signal by a known amount Δfs, so that the beat frequencies ofthe up and down chirps occur in different frequency bands, which can bepicked up, e.g., by the FFT component in processing system 250, in theanalysis of the electrical signal output by the optical detector 230. Insome embodiments, the RF signal coming out of the balanced detector isdigitized directly with the bands being separated via FFT. In someembodiments, the RF signal coming out of the balanced detector ispre-processed with analog RF electronics to separate a low-band(corresponding to one of the up chirp or down chip) which can bedirectly digitized and a high-band (corresponding to the opposite chirp)which can be electronically down-mixed to baseband and then digitized.Both embodiments offer pathways that match the bands of the detectedsignals to available digitizer resources. In some embodiments, themodulator 282 a is excluded (e.g., in direct ranging embodiments).

FIG. 2B is a block diagram that illustrates a simple saw tooth scanpattern for a hi-res Doppler system, used in some prior art embodiments.The scan sweeps through a range of azimuth angles (horizontally) andinclination angles (vertically above and below a level direction at zeroinclination). In various embodiments described below, other scanpatterns are used. Any scan pattern known in the art may be used invarious embodiments. For example, in some embodiments, adaptive scanningis performed using methods described in World Intellectual PropertyOrganization publications WO 2018/125438 and WO 2018/102188, the entirecontents of each of which are hereby incorporated by reference as iffully set forth herein.

FIG. 2C is an image that illustrates an example speed point cloudproduced by a hi-res Doppler LIDAR system, according to an embodiment.Each pixel in the image represents a point in the point cloud whichindicates range or intensity or relative speed or some combination atthe inclination angle and azimuth angle associated with the pixel

FIG. 2D is a block diagram that illustrates example components of a highresolution (hi res) LIDAR system 200′, according to an embodiment. In anembodiment, the system 200′ is similar to the system 200 with theexception of the features discussed herein. In an embodiment, the system200′ is a coherent LIDAR system that is constructed with monostatictransceivers. The system 200′ includes the source 212 that transmits thecarrier wave 201 along a single-mode optical waveguide over atransmission path 222, through a circulator 226 and out a tip 217 of thesingle-mode optical waveguide that is positioned in a focal plane of acollimating optic 219 or within about 100 microns (um) or within about0.1% to about 0.5% of a focal length of the collimating optic 219. Inone example embodiment, the collimating optic 219 includes doublets,aspheres or multi-element designs. In an embodiment, the carrier wave201 exiting the optical waveguide tip 217 is shaped by the optic 229into a collimated target beam 205′ which is scanned over a range ofangles 227 by scanning optics 218. In some embodiments, the carrier wave201 is phase or frequency modulated in a modulator 282 a upstream of thecollimation optic 229. In other embodiments, modulator 282 is excluded.In an embodiment, return beams 291 from an object are directed by thescanning optics 218 and focused by the collimation optics 229 onto thetip 217 so that the return beam 291 is received in the single-modeoptical waveguide tip 217. In an embodiment, the return beam 291 is thenredirected by the circulator 226 into a single mode optical waveguidealong the receive path 224 and to optical mixers 284 where the returnbeam 291 is combined with the reference beam 207 b that is directedthrough a single-mode optical waveguide along a local oscillator path220. In one embodiment, the system 200′ operates under the principalthat maximum spatial mode overlap of the returned beam 291 with thereference signal 207 b will maximize heterodyne mixing (opticalinterference) efficiency between the returned signal 291 and the localoscillator 207 b. This arrangement is advantageous as it can help toavoid challenging alignment procedures associated with bi-static LIDARsystems.

In some embodiments, the system 200′ includes more than one waveguidearranged in a waveguide array and where each waveguide in the array hasa tip that is positioned in a similar location as the tip 217 in FIG.2D. In one embodiment, each waveguide of the waveguide array has arespective circulator 226 and a respective optical mixer 284 to combinea respective return beam 291 with a respective reference beam 207 b. Inother embodiments, the system 200′ includes a fewer number ofcirculators 226 and optical mixers 284 than the number of waveguides sothat the system and the system is configured to switch between one ormore waveguides at respective time periods so that return beam 291 datafrom the one or more waveguides is combined at the optical mixers 284with one or more respective reference beams 207 b. This embodimentpermits a fewer number of processing channels (e.g. fewer number ofcirculators 226 and optical mixers 284) than the number of waveguides inthe array.

FIG. 2E is a block diagram that illustrates an example cross-sectionalside view of a collimator 231 used a LIDAR system, such as system 200 orsystem 200′, with a waveguide array 215 to form a collimated fan beam233, according to an embodiment. In an embodiment, the LIDAR systemincludes the waveguide array 215 of a plurality of optical waveguides225 a, 225 b, 225 c, 225 d, collectively referenced hereinafter aswaveguides 225. The tip 217 of each waveguide 225 a, 225 b, 225 c, 225 dis positioned in a similar manner as the tip 217 of the waveguide 225 ofFIG. 2D, e.g. in a focal plane of the collimating optic 229. In someembodiments, the beam 201 from the source 212 is divided by a splitterinto multiple waveguides 225 a, 225 b, 225 c, 225 d along thetransmission path 222 to multiple circulators 226 that direct the beam201 to the tips 217 of the waveguides 225 a, 225 b, 225 c, 225 d. Inother embodiments, multiple sources 212 are provided which generatemultiple beams 201 that are directed into the multiple waveguides 225.Return beams 291 from the waveguides 225 a, 225 b, 225 c, 225 d aretransmitted by the multiple circulators 226 to a respective one ofmultiple optical mixers 284, where each respective return beam 291 iscombined with a respective reference beam 207 b transmitted through oneof a plurality of optical waveguides (not shown) along the referencepath 220.

In one embodiment, the fan of collimated beams 233 is a set ofcollimated laser beams 236 a, 236 b, 236 c, 236 d, collectivelyreferenced hereinafter as laser beams 236, which can be used for ascanning LIDAR system. In one example embodiment, a desired beam 236diameter size is in a range from about 5 millimeters (mm) to about 12 mmand a desired angular separation between beams 236 is in a range fromabout 0.05 degrees to about 10 degrees. In an example embodiment, anangular spread of the fan of collimated beams 233 is about 2 degrees orin a range from about 0.5 degrees to about 4 degrees or in a range fromabout 0.05 degrees to about 10 degrees. In an embodiment, the fan ofindividual collimated beams 233 is generated by passing the divergingbeam 201 from the tips 217 of the array 215 through a single collimatingoptic 229. In some embodiments, beams 201 from each fiber 225 overlap atthe collimating optic 229, but emerge from the collimator 231 as theseparately collimated beams 236.

In one embodiment, the waveguide array 215 is one of a v-groove opticalfiber array, a multi-fiber connector (e.g. separate optical fibers inone connector), an optical fiber bundle (e.g. single optical fiber withmultiple cores), a planar lightwave circuit, or other arrangement ofclosely spaced optical waveguides 225. In some embodiments, a spacing221 between waveguides 225 is in a range from about 100 μm to about 1000μm. In one embodiment, the spacing 221 between waveguides 225 is aboutequal throughout the array 215. In other embodiments, the spacing 221between waveguides is irregular throughout the array 215 (e.g. thespacing 221 between waveguides 225 is adjusted based on an anticipatedtarget range of a certain angular region of the fan 233 associated withthose waveguides 225). In an example embodiment, the waveguide array 215is a v-groove fiber array where the spacing 221 is in a range from about125 μm to about 250 μm and the number of waveguides 225 is in a rangefrom about 2 to about 16. In some embodiments, the waveguides 225 arearranged in a linear fashion to form the array 215, however in otherembodiments the waveguides 225 are arranged in a two-dimensional fashionto form a two-dimensional array.

In an embodiment, the beams 201 are each emitted from the tips 217 ofthe waveguides 225 into a solid angle determined by one or more of thecross-sectional size of the waveguide 225 region, the waveguide 225materials, and/or the wavelength of the beam 201. In one embodiment, ALIDAR system is used with any light wavelength that is compatible withwaveguides 225, and any configuration of the waveguide 225. In oneexample embodiment, the wavelength of the beam 201 from the source 212is about 1550 nanometers (nm) and/or the waveguide 225 is single-modewith a 10 μm mode field diameter at the end face or tip 217 of thewaveguide 225.

FIG. 2F is a block diagram that illustrates an example of a ray diagramof the collimator 231 of FIG. 2E shaping one beam 236 a in thecollimated fan beam 233, according to an embodiment. In an embodiment,the collimating optics 229 are reflective or refractive. In one exampleembodiment, the collimating optics 229 in a reflective collimator 231 isa parabolic mirror. In another example embodiment, the collimatingoptics 229 in a refractive collimator 231 includes one or morerefractive lens elements. In an embodiment, the effective focal length235 of the optics 229 determines the collimated beam diameters 246 and,along with the fiber spacing 221, the angular spacing between thecollimated beams 236. In an embodiment, the beam diameter 246 depends onthe focal length 235, the wavelength of the beam 201 and a mode fielddiameter (MFD) of the waveguide 225 a, which is expressed in Equation 5below:

$\begin{matrix}{d = {1.22*( \frac{\lambda*{focal}\mspace{14mu} {length}}{MFD} )}} & (5)\end{matrix}$

where λ is the wavelength of the beam 201, MFD is the mode fielddiameter of the waveguide 225 a and the focal length is the focal length235 of the collimating optics 229. In an example embodiment, thewavelength is about 1500 nanometers (nm) or in a range from about 1400nm to about 1600 nm; the focal length is about 75 millimeters (mm) or ina range from about 50 mm to about 100 mm; and the MFD is about 10.5microns (μm) or in a range from about 8 μm to about 12 μm. In anembodiment, a spacing between the waveguide array 215 end face (e.g.tips 217 a, 217 b of the waveguides 225 a, 225 b) and the collimatingoptics 229 is designed to be about equal to the effective focal length235 of the collimating optics 229.

For purposes of this description, “about equal to” means that thespacing is within a threshold distance (e.g., about 100 μm) or within athreshold percentage of the focal length 235 (e.g. within about ±0.5% ofthe focal length). This advantageously achieves a high degree ofcollimation of the output beams 236. In some embodiments, forapplications where a set of converging beams 236 are desired, thedistance between the array 215 end face and the optics 229 is more thanthe focal length 235 (e.g. within about +0.5% of the focal length). Inother embodiments, for applications where a set of converging beams 236are desired, the distance between the array 215 end face and the optics229 is less than the focal length 235 (e.g. within about −0.5% of thefocal length). In some embodiments, it is desirable to have a slightlyconverging set of beams 236.

In some embodiments, an angle θ239 at which a particular beam 236 aexits the collimator 231 depends on a distance 228 separating thewaveguide tip 217 a from an optical axis 237 of the collimating optics229 and the effective focal length 235 of the collimating optics 229.This is expressed in Equation 6 below:

$\begin{matrix}{\theta = {\tan^{- 1}( \frac{y}{{focal}\mspace{14mu} {length}} )}} & (6)\end{matrix}$

where y is the separation distance 228, and focal length is the focallength 235 of the collimating optics 229.

In some embodiments, the arrangement depicted in FIG. 2F is applicableto a relatively simple collimating system with one or more opticalelements that can be modelled as a single element. In other embodiments,multiple optical elements achieve a shorter distance between thewaveguide tips 217 a, 217 b and the output of the collimator 231 whilemaintaining a desired output beam diameter 246. In one exampleembodiment, optics are included at the tips 217 of the waveguides 225 toincrease a divergence of each beam 201.

4. FAN BEAM SCANNING

Various embodiments of the scanning optics 218 are used to adjust thedirection of the fan of collimated beams 233 in one or more planes, asdescribed herein. FIG. 2G is a block diagram that illustrates examplecomponents to scan a direction of the collimated fan beam 233 of FIG. 2Eover a range of angles, according to an embodiment. FIG. 2H is a blockdiagram that illustrates a top view of the components of FIG. 2G,according to an embodiment. For purposes of FIGS. 2G-2H, the waveguides225 of the array 215 and the collimated fan of beams 233 are arranged ina first plane, e.g. the plane of FIG. 2G or perpendicular plane 234 inFIG. 2H. In an embodiment, a scanner 241 is provided that adjusts adirection of the collimated fan 233 in the first plane, e.g. in theplane of FIG. 2G to generate a modified collimated fan of beams 233′. Inone embodiment, the scanner 241 is any reflective or refractive opticthat is capable of adjusting the direction of the collimated fan 233 inthe first plane. In an example embodiment, the scanner 241 is agalvanometer, a microelectromechanical systems (MEMS) mirror, a voicecoil actuated mirror or another polygon scanner.

In an embodiment, a second scanner is also provided that adjusts adirection of the collimated fan of beams 233′ in a second plane that isdifferent from the first plane, e.g. a second plane that is differentfrom the plane of the figure in FIG. 2G. In one embodiment, the secondplane is about orthogonal (e.g. about 90 degrees±10 degrees) to thefirst plane, e.g. orthogonal to the plane of FIG. 2G or within the planeof FIG. 2H.

In one embodiment, the second scanner is a polygon scanner 244 with aplurality of facets 245 a, 245 b that rotates with an angular velocity249 about an axis of rotation 243. In one example embodiment, thepolygon scanner 244 rotates about the axis of rotation 243 with aconstant speed. In an example embodiment, the polygon scanner 244 hasone or more of the following characteristics: manufactured by Blackmore®Sensors with Copal turned mirrors, has an inscribed diameter of about 2inches or in a range from about 1 inch to about 3 inches, each mirror isabout 0.5 inches tall or in a range from about 0.25 inches to about 0.75inches, has an overall height of about 2.5 inches or in a range fromabout 2 inches to about 3 inches, is powered by a three-phase BrushlessDirect Current (BLDC) motor with encoder pole-pair switching, has arotation speed in a range from about 1000 revolutions per minute (rpm)to about 5000 rpm, has a reduction ratio of about 5:1 and a distancefrom the collimator 231 of about 1.5 inches or in a range from about 1inch to about 2 inches. As depicted in FIG. 2H, in one embodiment thepolygon scanner 244 is positioned so that the first plane 234 (e.g. theplane of FIG. 2G within which the waveguides 225 and collimated fan 233are arranged) intersects the axis of rotation 243 of the polygon scanner244. As depicted in FIG. 2G, in another embodiment, the waveguide array215 features waveguides 225 that are stacked in a direction (e.g.vertical direction in FIG. 2G) that is parallel to the axis of rotation243.

The intended application for LIDAR system including the collimator 231and the scanners 241, 244 is for a 3D LIDAR imaging system usingscanning laser beams. In an embodiment, one goal of the LIDAR imagingsystem is to provide as high a coverage of a scene (e.g., as manymeasured 3D points within a given field of view, or as small a distancebetween measured 3D points) in as short a time as possible. In oneembodiment, having multiple beams 236 within the collimated fan 233 thatscan simultaneously increases the coverage in a given amount of timecompared to having one beam, so having a multi-beam system is desirable.

In one embodiment, the collimated fan of beams 233′ is incident on thefacet 245 a of the polygon scanner 244 and is redirected by the facet245 a into a collimated fan of beams 233″ in the second plane. In oneembodiment, a first angle and a second angle of the polygon scannerdefines a scan pattern or swipe of the fan 233″ in the second plane andthe first and second angles are stored in memory 704 of the processingsystem 250. As the polygon scanner 244 and facet 245 a rotate, the fan233″ is redirected within the second plane from the first angle to thesecond angle to perform a swipe of the beam. In one embodiment, thelaser source 212 and the beam 201 remain on as the polygon scanner 244rotates between facets 245 a, 245 b and the processing system 250 istimed to only use the scan pattern or swipe of the fan 233″ between thefirst and second angle and to not use portions of the fan 233″ outsideof this angle range, e.g. portions of the fan 233″ that pass betweenfacets 245 a, 245 b. In this example embodiment, the processing system250 is timed so to only consider return beams 291 based on the scanpattern or swipe of the fan 233″ between the first and second anglesalong a respective facet 245 a, 245 b and not to consider return beams291 based on portions of the fan 233″ that pass between the facets 245a, 245 b, e.g. that pass over a facet edge between the facets 245 a, 245b. In this embodiment, the polygon scanner 244 continuously rotates at aconstant speed, in order to maximize efficiency of the LIDAR system. Inan embodiment, the LIDAR system performs multiple scan patterns orswipes of the beam and for each scan pattern the processing system 250is timed so to consider the fan 233″ being redirected from the firstangle to the second angle within the second plane on each respectivefacet 245 a, 245 b of the polygon scanner 244.

FIG. 4A is an image that illustrates an example of multiple interleaveswipes 442 a, 442 b of the collimated fan beam 233″ using the system ofFIG. 2G, according to an embodiment. In an embodiment, swipe 442 a is afirst swipe of the fan 233″ by the polygon scanner 244 in the secondplane from the first angle to the second angle. In one embodiment, afterperforming the first swipe 442 a, the first scanner 241 adjusts thedirection of the fan beam 233′ in the first plane by an incrementalangle 444. In an example embodiment, the incremental angle 444 for theinterleave swipes 442 a, 442 b is about 0.5 degrees or in a range fromabout 0.05 degrees to about 1 degrees or in a range from about 0.005degrees to about 2 degrees. In an example embodiment, the incrementalangle 444 is less than an angular spread of the fan beam 233′ in thefirst plane. In an embodiment, after the first scanner 241 adjusts thefan beam 233′ by the incremental angle 444, the polygon scanner 244performs a second swipe 442 b of the collimated fan beam 233″ in thesecond plane from the first angle to the second angle. A thirdinterleved swipe is indicated by the lightest lines in FIG. 4A. Althoughthree interleave swipes 442 a, 442 b and the lightest lines are depictedin FIG. 4A, more than three swipes can be interleaved in a similarmanner as discussed above with respect to the swipes 442 a, 442 b. Inone embodiment, the swipes 442 a, 442 b are interleaved based on thespacing 221 of the waveguides 225 in the array 215 being greater than athreshold spacing (e.g. about 500 μm or in a range from about 400 μm toabout 600 μm).

To perform the interleaving of the swipes 442 a, 442 b, the processingsystem 250 is timed to consider return beams 291 as the fan beam 233″ isscanned from the first angle to the second angle over the first swipe442 a; the processing system 250 then transmits a second signal to thescanner 241 to adjust the fan beam 233′ in the first plane by theincremental angle 444; and the processing system 250 is further timed toconsider return beams 291 as the fan beam 233″ is scanned from the firstangle to the second angle over the second swipe 442 b. In oneembodiment, the processing system 250 is timed so to consider the returnbeams 291 between respective initial and final times when the fan beam233″ is reflected off one of the facets 245 and is scanned from thefirst angle to the second angle in the second plane between the initialtime and the final time. One advantage of the interleaving of the beamswipes 442 a, 442 b is a higher resolution of return beam 291 data isachieved as compared to use of a single beam 291 (e.g. beam 205′ of FIG.2D).

FIG. 4B is an image that illustrates an example of multiple offsetswipes 442 a′, 442 b′, 442 c′ of the collimated fan beam 233″ using thescanning system of FIG. 2G, according to an embodiment. In anembodiment, swipe 442 a′ is a first swipe of the fan 233″ by the polygonscanner 244 in the second plane from the first angle to the secondangle. In one embodiment, after performing the first swipe 442 a′, thefirst scanner 241 adjusts the direction of the fan beam 233′ in thefirst plane by an incremental angle 444′. In an example embodiment, theincremental angle 444′ for the offset swipes 442 a′, 442 b′ is about 2.5degrees or selected in a range from about 1 degrees to about 4 degreesor selected in a range from about 0.5 degrees to about 6 degrees. In anexample embodiment, the incremental angle 444′ about equal to an angularspread of the fan beam 233′ in the first plane. In an embodiment, afterthe first scanner 241 adjusts the fan beam 233′ by the incremental angle444′, the polygon scanner 244 performs a second swipe 442 b′ of thecollimated fan beam 233″ in the second plane from the first angle to thesecond angle. The first scanner 214 then adjusts the fan beam 233′ bythe incremental angle 444′ before the polygon scanner 244 performs athird swipe 442 c′. Although three offset swipes 442 a′, 442 b′, 442 c′are depicted in FIG. 4B, more than three swipes can be offset in asimilar manner as discussed above with respect to the swipes 442 a′, 442b′, 442 c′. In one embodiment, the swipes 442 a′, 442 b′, 442 c′ areoffset based on the spacing 221 of the waveguides 225 in the array 215being less than a threshold spacing (e.g. about 100 μm or in a rangefrom about 80 μm to about 120 μm).

To perform the offset swipes 442 a′, 442 b′, 442 c′, the processingsystem 250 is timed to consider return beams 291 as the fan beam 233″ isscanned from the first angle to the second angle over the first swipe442 a′; the processing system 250 then transmits a second signal to thescanner 241 to adjust the fan beam 233′ by the incremental angle 444′;and the processing system 250 is further timed to consider return beams291 as the fan beam 233″ is scanned from the first angle to the secondangle over the second swipe 442 b′. The processor is similarly timed toconsider return beams 291 when the polygon scanner 244 scans the fanbeam 233″ from the first angle to the second angle over the third swipe442 c′. One advantage of offsetting the beam swipes 442 a′, 442 b′, 442c′ is faster filling of a field of view as compared to use of a singlebeam 291 (e.g. beam 205′ of FIG. 2D) or interleaving as depicted in FIG.4A.

FIG. 4C is an image that illustrates an example of one swipe 442″ of thecollimated fan beam 233″ using the system of FIG. 2G where thewaveguides 225 in the array 215 are irregularly spaced, according to anembodiment. In an embodiment, the swipe 442″ includes a first pluralityof beams 446 a with a first spacing 448 a; a second plurality of beams446 b with a second spacing 448 b; and a third plurality of beams 446 cwith a third spacing 448 c, where the third spacing 448 c is greaterthan the second spacing 448 b and the second spacing 448 b is greaterthan the first spacing 448 a. In an example embodiment, the firstspacing 448 a is about 0.1 degrees or in a range from about 0.05 degreesto about 0.15 degrees. In an example embodiment, the second spacing 448b is about 0.2 degrees or in a range from about 0.1 degrees to about 0.3degrees. In an example embodiment, the third spacing 448 c is about 0.4degrees or in a range from about 0.3 degrees to about 0.5 degrees.

In an embodiment, the first plurality of beams 446 a are attributable toa first plurality of waveguides 225 having a first spacing 221 a; thesecond plurality of beams 446 b are attributable to a second pluralityof waveguides 225 having a second spacing 221 b; and the third pluralityof beams 446 c are attributable to a third plurality of waveguides 225having a third spacing 221 c, where the third spacing 221 c is greaterthan the second spacing 221 b and the second spacing is greater than thefirst spacing 221 a. In an example embodiment, the first spacing 221 ais about 100 μm or in a range from about 80 μm to about 120 μm, thesecond spacing 221 b is about 200 μm or in a range from about 160 μm toabout 240 μm and the third spacing 221 c is about 400 μm or in a rangefrom about 320 μm to about 480 μm. Although FIG. 4C depicts threedifferent regions of the swipe 442″ with different beam spacing in eachregion, the invention is not limited to three different regions and cangenerate less or more than three regions of the swipe with differentbeam spacing.

In another embodiment, the spacing 221 of the array 215 is adjusted sothat the spacing 448 of each region 446 of the swipe 442″ is based on atarget range corresponding to that region 446. In an example embodiment,a region 446 a with smaller spacing 448 a between the beams is arrangedso that the region 446 a of the swipe 442″ corresponds with large targetrange (e.g. over 100 m or beam 344 in FIG. 3B) whereas a region 446 cwith larger spacing 448 c is arranged so that the region 446 ccorresponds with smaller target range (e.g. less than 100 m or beams342, 346 in FIG. 3B). In another example embodiment, the beam fan 233″forming the swipe 442″ provides denser coverage at longer ranges (e.g.larger angular spread for beams 342 directed towards the surface 349just in front of the vehicle 310 and smaller angular spread for beams344 that are about parallel to the direction of travel 313 of thevehicle 310, as depicted in FIG. 3B).

FIG. 6A is a flow chart that illustrates an example method 600 foroperating a scanner of a LIDAR system. Although steps are depicted inFIG. 6A, and in subsequent flowcharts FIGS. 6B and 6C as integral stepsin a particular order for purposes of illustration, in otherembodiments, one or more steps, or portions thereof, are performed in adifferent order, or overlapping in time, in series or in parallel, orare omitted, or one or more additional steps are added, or the method ischanged in some combination of ways.

In step 601, a plurality of beams are generated using a waveguide arrayarranged in a first plane, where each beam is transmitted from arespective waveguide in the array. In an embodiment, in step 601 theplurality of beams 201 are generated using the waveguide array 215arranged in the first plane (e.g. plane of FIG. 2E/2G or plane 234 ofFIG. 2H), where each beam 201 is transmitted from a respective tip 217of a waveguide 225 of the array 215. In one example embodiment, in step601 the processing system 250 transmits a signal to the source 212 totransmit one beam 201 that is split into multiple beams that are coupledinto each waveguide 225 of the array 215. In another example embodiment,in step 601 the processing system transmits a signal to multiple sources212 where each source 212 transmits a respective beam 201 that iscoupled into each respective waveguide 225 of the array 215.

In step 603, the beams generated in step 601 are shaped with acollimator into a fan of collimated beams that have an angular spread inthe first plane. In an embodiment, in step 603 the beams 201 generatedwith the waveguide array 215 are shaped with the collimator 231 into thefan 233 of collimated beams 236, where the fan 233 has an angular spreadin the first plane. In an example embodiment, the fan 233 has an angularspread in the same first plane (e.g. plane of FIG. 2G) that thewaveguides 225 are arranged in the array 215. In another embodiment, instep 603 one or more of the position of the tips 217 of the waveguidearray 215 relative to the focal plane of the collimating optics 229, thefocal length 235, the spacing 221 between the waveguides 225 anddistance 228 separating the waveguide 225 from the optical axis 237 areadjusted to achieve the fan 233 with a desired angular spread and beamdiameter 246. In some embodiments, one or more of these parameter valuesare mechanically engineered. In other embodiments, other devices (e.g.switch network) acting behind the waveguides 225 can be used toelectronically control the outputs to the multiple waveguides 225.

In step 605, a first angle and a second angle are received that definean angle range of a scan pattern or swipe of the fan 233 in a secondplane that is different from the first plane. In an embodiment, in step605 a first angle and a second angle are input using an input device 712and/or a pointing device 716 and/or received over a network link 778 ofthe processing system 250 and stored in the memory 704 of the processingsystem 250. In an example embodiment, the first angle and the secondangle define the initial and final angle through which the fan 233″ isswept in the second plane (e.g. plane of FIG. 2H) by the polygon scanner244. In an example embodiment, the angle range of the scan pattern orswipe is about 20 degrees or in a range from about 15 degrees to about25 degrees and the first angle is about −15 degrees or within a rangefrom about −20 degrees to about −10 degrees and the second angle isabout +5 degrees or within a range from about 0 degrees to about +10degrees, where the first angle and the second angle are measured withrespect a normal to the plane 234. In other embodiments, the angle rangedepends on the angular spread of the fan 233 so that the bottom of thefan 233 at the first angle (e.g. lowest swipe angle) and the top of thefan 233 at the second angle (e.g. highest swipe angle) covers a verticalfield of view (FOV) of interest.

In step 607, the direction of the fan is adjusted in the second planefrom the first angle to the second angle using a second scanner. In anexample embodiment, step 607 is performed with the polygon scanner 244so that the fan 233″ is adjusted in the second plane from the firstangle to the second angle using the polygon scanner 244 that rotatesabout the axis of rotation 243 with the constant speed. In an exampleembodiment, in step 607 the processing system 250 is timed so toconsider return beams 291 when the polygon scanner 244 scans the fan233″ from the first angle to the second angle within the second planebetween the initial and final time. In an embodiment, the processingsystem 250 is timed to reject return beams 291 that are received whenthe fan 233″ is scanned over angles outside the angle range definedbetween the first angle and the second angle within the second plane. Inan example embodiment, for interleaving swipes, in step 607 the polygonscanner 244 scans the fan 233″ from the first angle to the second angleto form swipe 442 a. In another example embodiment, for offset swipes,in step 607 the polygon scanner 244 scans the fan 233″ from the firstangle to the second angle to form swipe 442 a′. In still otherembodiments, in step 607 for swipes with irregular beam spacing, in step607 the polygon scanner 244 scans the fan 233″ from the first angle tothe second angle to form swipe 442″. In this example embodiment, forswipes with the irregular beam spacing, steps 609, 611 can be omitted.In other embodiments, for swipes with the irregular beam spacing, steps609, 611 are performed as described below.

In step 609, the direction of the fan is adjusted in the first plane byan incremental angle based on a spacing of the waveguides in the array.In an embodiment, in step 609, the direction of the fan 233″ in thefirst plane is adjusted by the scanner 241 by the incremental angle 444,444′ based on the spacing 221 of the waveguides 225 in the array 215. Inan example embodiment, in step 609, the incremental angle 444 is usedfor interleaving swipes. In another example embodiment, in step 609, theincremental angle 444′ is used for offset swipes. In one embodiment,step 609 is performed after step 607. In another embodiment, in step 609the processing system 250 transmits a signal to the scanner 241 toadjust the direction of the fan 233′ in the first plane by theincremental angle 444, 444′. In other embodiments, step 609 is notperformed by the scanner 241 but instead is performed by using differentangled facets 245 of the polygon scanner 244 for repeated iterations ofstep 607, where the facets 245 are angled differently with respect tothe axis of rotation 243. In an example embodiment, a first polygonfacet 245 a is used in a first iteration of step 607 to perform thefirst swipe 442 a and a second polygon facet 245 b is used in a seconditeration of step 607 to perform the second swipe 442 b, where thesecond polygon facet 245 b is angled differently than the facet 245 awith respect to the axis of rotation 243 so to adjust the swipe 442 b bythe incremental angle 444. In one embodiment, adjacent facets 245 of thepolygon scanner 244 are angled at differing increments with respect tothe axis of rotation 243. In an example embodiment, the differingincrement is in a range from about 3 degrees to about 7 degrees. Inanother example embodiment, each adjacent facet 245 has a differingincrement so that the total range of angular increments is in a rangefrom about 15 degrees to about 35 degrees over the polygon scanner 244.

In step 611, a determination is made of how many swipes of the fan havebeen performed. In an example embodiment, the determination in step 611is based on a stored field in the memory 704 of the processing system250, where the stored field is a counter that is incremented for eachiteration of step 607. Additionally, in step 611 the processing system250 compares the determined number of swipes with a desired number ofswipes (e.g. two, four, etc.). If the determined number of swipes isless than the desired number of swipes, the method 600 moves back tostep 607. If the determined number of swipes is equal to the desirednumber of swipes, the method ends. In an example embodiment where thedesired number of swipes is four, step 611 will move the method 600 backto step 607 three times until in step 611 it is determined that thenumber of swipes equals the desired number of swipes and the method 600ends.

5. STEP SCANNING OF FAN BEAM

In an embodiment, due to round trip delay of the return beam 291, thereceive mode of the return beam 291 will laterally shift or “walk off”from the transmitted mode of the transmitted beam 205′ when the beam isbeing scanned by the scanning optics 218. For the waveguide array 215 ofFIG. 2G, the return beam 291 can laterally shift or “walk off” from thetransmitted beam 201 at the tip 217 of each respective waveguide 225.FIG. 5A is an image that illustrates an example of beam walkoff forvarious target ranges and scan speeds in the system 200″ of FIG. 2G,according to an embodiment. The horizontal axis 502 indicates targetrange and the vertical axis 522 indicates scan speed of the beam usingthe scanning optics 218 (e.g. scanner 241, polygon scanner 244). As FIG.5A depicts, there is no beam walkoff when the beam is not scanned(bottom row) since the image 518 a of the focused return beam 291 iscentered on the fiber tip 217 demonstrating no beam walkoff at shorttarget range and the image 518 b of the focused return beam 291 is alsocentered on the fiber tip 217 demonstrating no beam walkoff at fartarget range. When the beam is scanned at a moderate scan speed (middlerow in FIG. 5A), a moderate beam walkoff 519 a is observed between theimage 518 a of the focused return beam 291 and the fiber tip 217 and alarger beam walkoff 519 b is observed between the image 518 b of thefocused return beam 291 and the fiber tip 217. When the beam is scannedat a high scan speed (top row in FIG. 5A), a beam walkoff 521 a isobserved at short range that exceeds the beam walkoff 519 a at themoderate scan speed and a beam walkoff 521 b is observed at large rangethat exceeds the beam walk off 519 b at the moderate scan speed. Thus,the beam walkoff increases as the target range and scan speed increase.In an embodiment, increased target range induces a time delay duringwhich the image 518 a, 518 b shifts away from the tip 217 of the fibercore. Thus, in some embodiments, the LIDAR is operated to account forthis walkoff appropriately. In one embodiment, such an operation limitsthe beam walkoff 519 based on a diameter of the image 518 (e.g. nogreater than half of the diameter of the image 518).

FIG. 5B is a graph that illustrates an example of coupling efficiencyversus target range for various scan rates in a LIDAR system, accordingto an embodiment. The horizontal axis 502 indicates target range inunits of meters (m) and the vertical axis 530 indicates couplingefficiency which is unitless. In an embodiment, the coupling efficiencyis inversely proportional to the beam walkoff 519. A first trace 532 adepicts the coupling efficiency of the focused return beam 291 into thefiber tip 217 for various target ranges based on no scanning of thebeam. The coupling efficiency remains relatively high and constant for awide range of target ranges. A second trace 532 b depicts the couplingefficiency of the focused return beam 291 into the fiber tip 217 forvarious target ranges based on moderate scan rate of the beam. In anembodiment, the coupling efficiency at the moderate scan rate peaks at amoderate target range (e.g. about 120 m) and then decreases as targetrange increases. A third trace 532 c depicts the coupling efficiency ofthe focused return beam 291 into the fiber tip 217 for various targetranges based on a high scan rate of the beam. In an embodiment, thecoupling efficiency of the high scan rate peaks at a low target range(e.g. about 80 m) and then decreases as target range increases.

It is here recognized that beam walk off 519, 521 is avoided andcoupling efficiency (and signal to noise ratio or SNR) are optimizedwhen there is no scanning or when the scan rate is minimized. Thus, ascan pattern was developed for the collimated fan 233″ in the system ofFIG. 2G from the first angle to the second angle within the second planeusing a step scan. In an embodiment, the step scan stops the fan 233″ atone or more incremental angles between the first and second angle for aminimum time period. In an example embodiment, the incremental anglesbetween the first and second angle are those angles at which LIDAR data(e.g. return beams 291) is desired. In an embodiment, the minimum timeperiod is adjusted based on a return trip time of the return beam 291from the target and a duration of a waveform in the return beam 291(e.g. duration of a pulse waveform) to ensure that the waveform of thereturn beam 291 is received at each waveguide tip 217 before thewaveguide is moved to the next angle. In another embodiment, the stepscan maximizes the scan rate for those angles between the incrementalangles, so to maximize the time efficiency of the scan pattern. Thisstep scan simultaneously maximizes the coupling efficiency and timeefficiency of the scan pattern.

In an embodiment, the system of FIGS. 2G-2H includes a second scanner252 that adjusts the fan 233″ in the second plane (e.g. plane of FIG.2H), in addition to the polygon scanner 244. In an example embodiment,the polygon scanner 244 has a larger field of view (FOV) than the secondscanner 252. In another example embodiment, the second scanner 252 is asilicon photonics based optical phased array with fast but minimaltenability. FIG. 4G is a graph that illustrates an example of scandirection of the fan 233″ in the second plane based on the scanners 244,251 in the system of FIG. 2H, according to an embodiment. A first trace435 indicates an adjusted direction of the fan 233″ in the second planebased on the polygon scanner 244. The horizontal axis 430 indicates timein arbitrary units and the vertical axis 432 indicates the direction ofthe fan 233″ in the second plane that is attributable to the polygonscanner 244. In an embodiment, since the polygon scanner 244 rotates ata constant speed, the trace 435 indicates a constant scan rate of thefan 233″ in the second plane from the first angle (e.g. at t=0) to thesecond angle (e.g. at some time t). The constant scan rate of the fan233″ based on trace 435 would reduce the coupling efficiency and SNR ofthe return beam 291, since it would introduce walk off 519, 521 (e.g.when the constant scan rate exceeds a threshold rate for walk off). Thusa further adjustment is made as described next.

A second trace 437 indicates an adjusted direction of the fan 233″ inthe second plane based on the second scanner 252. The second trace 437is advantageously selected so that when combined with the first trace435, the net adjusted direction of the fan 233″ in the second plane is astep scan with optimized parameters. The horizontal axis 430 indicatestime in arbitrary units and the vertical axis 434 indicates thedirection of the fan 233″ in the second plane that is attributable tothe second scanner 252. In an embodiment, the trace 437 is a sawtoothpattern with a frequency in a range from about 5 Hertz (Hz) to about 25Hz and an angular range (e.g., separation between the maximum andminimum angle) in a range from about 15 degrees to about 35 degrees. Inother embodiments, a sinusoidal, triangular or other arbitrary patternis used instead of the sawtooth pattern trace 437, provided that theother pattern encourages more density at the middle of the angularrange. In one embodiment, the sawtooth pattern of trace 437 features anangled portion and a vertical portion, where the angled portion runs inan opposite direction to the direction of trace 435 for the same timeincrement. In one example embodiment, the slope of the angled portion isselected to be equal and opposite to the slope of trace 435 so toachieve the flat portion of the step scan over the time duration 450.

A third trace 439 indicates a net adjusted direction of the fan 233″ inthe second plane based on the polygon scanner 244 and the second scanner252, e.g. based on combination of scans 435, 437. The vertical axis 436indicates the net adjusted direction of the fan 233″ in the secondplane. In an embodiment, the step scan of trace 439 includes steps witha time duration 450 and an angular increment 454 height. In an exampleembodiment, the angular increment 454 is in a range from about 0.05degrees to about 0.2 degrees. In an embodiment, the step scan of trace439 indicates that the scan angle of the fan 233″ is stopped atincremental angles (e.g. angles that are separated by angular increments454) between the first angle and the second angle for the time duration450. Additionally, in an embodiment, the step scan of trace 439indicates that the scan rate is maximized between the incrementalangles. This advantageously maximizes the collection efficiency and SNRof the return beam 291 received at each incremental angle while at thesame time maximizing the time efficiency of the scan pattern.

In an embodiment, the angular increment 454 is selected so that returnbeam 291 data is obtained at a desired angular resolution between thefirst and second angle over the second plane. In another embodiment, thetime duration 450 is selected to provide sufficient time to transmit thebeam 201 from the waveguide array 215, receive an initial portion of thereturn beam 291 and receive a remaining portion of the return beam 291at the waveguide tip 217. FIG. 4F depicts one embodiment where the timeduration 450 is adjusted based on a sum of the return trip time 420(e.g. based on a transmit time 424 and a return time 426 of the initialportion of the return beam 291) and an additional time 422 that is basedon a duration of the waveform in the return beam 291. Thisadvantageously ensures that a waveform in the return beam 291 isreceived at each waveguide tip 217 before the fan 233″ is moved from afirst incremental angle to a second incremental angle of the step scan.

FIG. 6B is a flow chart that illustrates an example method 630 foroperating a scanner of a LIDAR system, according to an embodiment. Steps631, 633 and 635 are similar to steps 601, 603, 605.

In step 637, the direction of the fan 233″ is simultaneously adjusted inthe second plane using the polygon scanner 244 and the second scanner252. In an embodiment, in step 637 the processing system 250 transmitssignals to the polygon scanner 244 and the second scanner 252, where thesignal to the polygon scanner 244 causes the scanner 244 to rotate atthe constant speed and the signal to the scanner 252 causes the scanner252 to adjust a direction of the fan 233″ in the second plane, e.g.based on the sawtooth trace 437.

In step 639, at incremental angles of the step function between thefirst angle and the second angle, the beam 201 is transmitted from thewaveguides of the array 215 and the return beam 291 is received at thewaveguides of the array 215. In an embodiment, the incremental anglesare defined by the angular increments 454 of the step scan trace 439. Inone embodiment, the scan of the fan 233″ commences at the first angle.The fan 233″ is scanned at a maximum scan rate between the first angleand a first incremental angle, based on the step scan trace 439. At thefirst incremental angle, the fan 233″ is held at the first incrementalangle for the time duration 450. In an embodiment, the source 212 andthe beam 201 remain on during the step scan trace 439. In an exampleembodiment, the processing system 250 is timed to exclude return beams291 received between the angular increments 454 and to consider returnbeams 291 received during the time durations 450 at each angularincrement 454 of the step scan trace 439. The return beam 291 isreceived at the tip of the waveguide array 215 over the time duration450. In an embodiment, after the time duration 450, the fan 233″ isre-scanned at the maximum scan rate from the first incremental angle bythe angular increment 454 to a second incremental angle. In an exampleembodiment, the fan 233″ stays at the second incremental angle for thetime duration 450 and the processing system 250 is timed to considerreturn beams 291 received over the time duration 450. This is repeatedfor each incremental angle between the first angle and the second angleover the second plane.

In step 641, it is determined whether additional scans or swipes of thefan 233″ are to be performed. The determination in step 641 is based oncomparing a completed number of swipes of the fan 233″ with a desirednumber of swipes of the fan 233″. In an example embodiment, thecompleted number of swipes of the fan 233″ is a counter that is storedin the memory 704 of the processing system 250 and is incremented foreach iteration of step 639. In another example embodiment, the desirednumber of swipes of the fan 233″ is a stored number in the memory 704.If the determination in step 641 is positive, the method 630 moves toblock 637. If the determination in step 641 is negative, the method 630ends. In some embodiments, step 609 of method 600 can be employed in themethod 630 so that the method 630 can be used to perform interleave oroffset swipes.

6. SCANNING WITH OPTICAL SWITCHES

In some embodiments, the LIDAR system features fewer processing channels(e.g. number of circulators 226, optical mixers 284, number ofwaveguides within the paths 220, 222, 224) than the number of waveguides225 in the array 215. This advantageously permits the LIDAR system to besimpler and more cost efficient. However, in order to process returnbeam 291 data from multiple waveguides 225 of the array 215 in thissystem, the system switches between one or more waveguides 225 in thearray 215 at respective time periods, so that the number of waveguides225 being used to transmit the beam 201 and receive the return beam 291does not exceed the number of processing channels.

In an embodiment, optical switches are used to direct light to any ofthe waveguides 225 individually for a temporal serialization ofmeasurements at each waveguide tip 217. This advantageously allows adistribution of LIDAR resources across space with near instantaneousswitching between angular measurement directions. In an exampleembodiment, fast optical switches with sub 50 nanosecond switch time areemployed. This switch time is much shorter than measurement integrationtimes used in many applications. In another example embodiment,integrated photonics platforms can also form the basis of low lossswitches using multi-mode interference structures to appropriate phasecontrol of inputs.

FIG. 2I is a block diagram that illustrates example optical switches 247used in the system of FIG. 2G to switch between one or more waveguides225 of the array 215, according to an embodiment. In one embodiment,each optical switch 247 is an MMI switch that is coupled to a phaseshifter. A first pair of switches 247 a, 247 b are selectivelyactivated, to route the beam 201 to either the waveguides 225 a, 225 b(e.g. switch 247 a) or to the waveguides 225 c, 225 d (e.g. switch 247b). A second pair of switches 247 c, 247 d are selectively activated toroute the beam 201 to either the waveguide 225 a (e.g. switch 247 c) orwaveguide 225 b (e.g. switch 247 d). A third pair of switches 247 e, 247f are selectively activated to route the beam 201 to either thewaveguide 225 c (e.g. switch 247 e) or waveguide 225 d (e.g. switch 247f).

In an example embodiment, the switch 247 is activated based on a signaltransmitted to the switch 247 from the processing system 250. In oneexample embodiment, the LIDAR system transmits the beam 201 through thewaveguide 225 a over a first time period by the processing system 250transmitting a signal to a first plurality of switches (e.g. switches247 a, 247 c) over the first time period. During the first time period,the beam 201 is transmitted from the tip 217 of the first waveguide 225a and a return beam 291 is received at the tip of the first waveguide225 a. Similarly, in another example embodiment, the LIDAR systemtransmits the beam 201 through the waveguide 225 b over a second timeperiod (e.g. after the first time period) by the processing system 250transmitting a signal to a second plurality of switches (e.g. switches247 a, 247 d) over the second time period. The beam 201 is thentransmitted from the tip 217 of the second waveguide 225 b and thereturn beam 291 is received at the tip 217 of the second waveguide 225 bover the second time period. The system can similarly switch between oneor more waveguides 225 over respective time periods, in order totransmit the beam 201 and receive the return beam 291 from the one ormore waveguides 225 over the respective time periods.

FIG. 4F is a graph that illustrates an example of a time axis 410indicating the switch time values between adjacent waveguides 225,according to an embodiment. The activation time 424 indicates when thefirst time period commences that the first waveguide 225 a is activated,e.g. the processing system 250 transmits the signals to the switches 247a, 247 c at the activation time 424. The beam 201 is transmitted fromthe tip 217 of the first waveguide 225 a beginning at the activationtime 424. A return trip time 420 is waited for a first portion of thereturn beam 291 to be received at the tip 217 of the first waveguide 225a at the return time 426. A waveform time 422 is then waited which isbased on a duration of the waveform of the return beam 291 (e.g. 3.6μsec) until a switch time 428 is reached which is the time when thesystem 200″ switches from the first waveguide 225 a to the secondwaveguide 225 b.

Thus, in one embodiment, the first time period that the first waveguide225 a remains activated is a sum of the return trip time 420 and theduration of the beam (e.g. waveform time 422). In an example embodiment,after the first time period, the processing system 250 transmits signalsto switches 247 a, 247 c to deactivate waveguide 225 a and transmitssignals to switches 247 a, 247 d over a second time period to activatethe waveguide 225 b, where the duration of the second time period isabout equal to the duration of the first time period. In an embodiment,the system 200″ switches between each waveguide 225 of the array 215 inthis manner. In other embodiments, the system 200″ switches between morethan one waveguide 225 at a time, where the time period that thewaveguides 225 remain active is about equal to the first time periodabove. In these embodiments, the system 200″ features more than oneprocessing channels (e.g. more than one circulator 226, mixer 284,etc.). In another embodiment, the switch time (e.g. about 50nanoseconds) between the end of the first time period and commencementof the second period is less than an integration time of the return beam291 in the LIDAR system, so not to incur a duty cycle penalty duringswitching.

In an embodiment involving optical switches, a slow mechanical scanneris paired with a switched array arranged orthogonally to the scandirection. In one embodiment, the scanner 241 of FIG. 2G is a slowmechanical scanner that adjusts a gross trajectory of the fan beam 233in a two dimensional space defined by the first plane (e.g. plane ofFIG. 2G) and the second plane (e.g. plane that is orthogonal to theplane of FIG. 2G), while the fan beam 233 angular spread remains in thefirst plane or aligned in a plane that is parallel to the first plane.In this embodiment, the polygon scanner 244 is omitted. In an exampleembodiment, the slow mechanical scanner 241 is one of a galvanometer, aMEMS mirror and a voice coil based steering mirror.

FIG. 4D is a graph 400 that illustrates a gross trajectory 406 of acollimated fan beam 233 scanned with the mechanical scanner 241,according to an embodiment. The horizontal axis 402 indicates thedirection or angle of the fan beam 233 in the first plane (e.g. plane ofFIG. 2G). The vertical axis 404 indicates the direction or angle of thefan beam 233 in the second plane (e.g. plane that is perpendicular toFIG. 2G). FIG. 4E is a graph that illustrates the gross trajectory 406of FIG. 4D and return beam data 410 received from the waveguide array215 based on switching between waveguides 225, according to anembodiment. In an embodiment, the scanner 241 commences to adjust afirst component of the trajectory 406 (e.g. angle of the fan 233 in thefirst plane) and a second component of the trajectory 406 (e.g. angle ofthe fan 233 in the second plane). During the adjustment of the fan 233along the trajectory 406 by the scanner 241, the fan 233 remainsparallel to the first plane. At each incremental position along thetrajectory 406, the LIDAR system switches between one or more waveguides225 in the array 215 so to collect return beam 291 data over the angularspan 410 of the fan 233 at each incremental position.

In an embodiment, the trajectory 406 of FIG. 4D demonstrates the grossscan trajectory of the mechanical scanner 241. In an embodiment, thearray of dots 410 demonstrates the various points which would beaccessed by sequentially switching between lateral positions (e.g.switching between waveguides 225) during the course of the verticalscan. In an embodiment, FIG. 4E shows that a reasonable grid of pointscan be synthesized by this approach. To make the approach work with amechanical scanner 241 that is also scanning laterally, a subset of theswitch nodes would be utilized at any position. This subset could beshifted laterally to counteract the motion of the gross scanning. Theresult would be rectangular grids of sample regions.

FIG. 6C is a flow chart that illustrates an example method 650 foroperating a scanner of a LIDAR system, according to an embodiment. In anembodiments, steps 651, 653, 655 are similar to steps 601, 603, 605.

In step 657, the scanner 241 adjusts a first component of the trajectory406 (e.g. angle of the fan 233 in the first plane) by a firstincremental angle over an incremental time period. In an embodiment, thefirst incremental angle is in a range from about 0.05 degrees to about0.2 degrees. In step 659, the scanner 241 adjusts a second component ofthe trajectory 406 (e.g. angle of the fan 233 in the second plane) by asecond incremental angle over the incremental time period. In anembodiment, the second incremental angle is in a range from about 0.05degrees to about 0.5 degrees. In an embodiment, in step 657 and 659, theprocessing system 250 transmits one or more signals to the scanner 241so that the first and second component of the trajectory 406 areadjusted. In other embodiments, the processing system 250 transmits onesignal to the scanner 241 to commence the adjustment over the trajectory406. In an embodiment, the second incremental angle is greater than thefirst incremental angle. In another embodiment, the ratio of the secondincremental angle to the first incremental angle is at least 2 or atleast 5 or at least 10.

In step 661, after the scanner 241 adjusts the trajectory 406 in steps657 and 659, the LIDAR system switches between each waveguide 225 in thearray 215 over a respective time period, so that the beam 201 istransmitted from each waveguide tip 217 and the return beam 291 isreceived at each waveguide tip 217 over the respective time period. Inan example embodiment, the processing system 250 transmits one or moresignals to switches 247 to switch between each waveguide 225. In anembodiment, a speed of the scanner 241 is sufficiently slow that step661 can be performed to switch between each waveguide 225 of the array215 before the scanner 241 re-adjusts the trajectory 406 to a differentlocation along the trajectory 406. In an example embodiment, the speedof the scanner 241 is in a range from about 500 degrees per second toabout 1000 degrees per second or further in a range from about 200degrees per second to about 1500 degrees per second.

In step 663, it is determined whether the second component of thetrajectory 406 (e.g. angle of the fan 233 in the second plane) reachedeither the first angle or second angle received in step 655. In anembodiment, the scanner 241 transmits data to the processing system 250including the angle of the fan 233 in the second plane at each locationalong the trajectory 406 and the processing system 250 compares thisangle with the first angle and second angle stored in a memory 704 ofthe processing system 250. If the received angle does not correspondwith the first or second angle, the method 650 moves back to block 657.This indicates that the second component of the trajectory 406 (e.g.vertical 404) has not yet reached the first angle or second angle (e.g.0 degrees or 7.5 degrees in FIG. 4D). Thus, the method 650 moves back toblock 657 so that the scanner 241 continues to adjust the trajectory406. If the received angle corresponds with the first angle or secondangle, the method 650 moves to block 665 where it is determined whetherthe fan 233 has yet to be scanned through a predetermined number ofswipes. In an example embodiment, in step 655, when it determined instep 663 that the received angle corresponds with the first angle orsecond angle, the processing system 250 increments a counter of a numberof swipes of the fan 233 stored in the memory 704. In step 665, theprocessor 250 determine whether the number of swipes stored in thememory 704 is less than a predetermined number of swipes stored in thememory. If the determination in step 665 is affirmative, the method 650moves back to block 657. If the determination in step 665 is negative,the method 650 ends. In an example embodiment, FIG. 4D depicts fourswipes of the fan 233 between the first and second angles along thevertical axis 404.

7. VEHICLE CONTROL OVERVIEW

In some embodiments a vehicle is controlled at least in part based ondata received from a hi-res Doppler LIDAR system mounted on the vehicle.

FIG. 3A is a block diagram that illustrates an example system 301 thatincludes at least one hi-res Doppler LIDAR system 320 mounted on avehicle 310, according to an embodiment. In an embodiment, the LIDARsystem 320 is similar to one of the LIDAR systems 200, 200′, 200″. Thevehicle has a center of mass indicted by a star 311 and travels in aforward direction given by arrow 313. In some embodiments, the vehicle310 includes a component, such as a steering or braking system (notshown), operated in response to a signal from a processor, such as thevehicle control module 272 of the processing system 250. In someembodiments the vehicle has an on-board processor 314, such as chip setdepicted in FIG. 8. In some embodiments, the on-board processor 314 isin wired or wireless communication with a remote processor, as depictedin FIG. 7. In an embodiment, the processing system 250 of the LIDARsystem is communicatively coupled with the on-board processor 314 or theprocessing system 250 of the LIDAR is used to perform the operations ofthe on board processor 314 so that the vehicle control module 272 causesthe processing system 250 to transmit one or more signals to thesteering or braking system of the vehicle to control the direction andspeed of the vehicle. The hi-res Doppler LIDAR uses a scanning beam 322that sweeps from one side to another side, represented by future beam323, through an azimuthal field of view 324, as well as through verticalangles (FIG. 3B) illuminating spots in the surroundings of vehicle 310.In some embodiments, the field of view is 360 degrees of azimuth. Insome embodiments the inclination angle field of view is from about +10degrees to about −10 degrees or a subset thereof.

In some embodiments, the vehicle includes ancillary sensors (not shown),such as a GPS sensor, odometer, tachometer, temperature sensor, vacuumsensor, electrical voltage or current sensors, among others well knownin the art. In some embodiments, a gyroscope 330 is included to providerotation information.

FIG. 3B is a block diagram that illustrates an example system 301′ thatincludes at least one hi-res LIDAR system 320 mounted on the vehicle310, according to an embodiment. In an embodiment, the LIDAR system 320is similar to the system 200 or system 200′ or system 200″. In oneembodiment, the vehicle 310 moves over the surface 349 (e.g. road) withthe forward direction based on the arrow 313. The LIDAR system 320 scansover a range of angles 326 from a first beam 342 oriented at a firstangle measured with respect to the arrow 313 to a second beam 346oriented at a second angle measured with respect to the arrow 313. Inone embodiment, the first angle and the second angle are vertical angleswithin a vertical plane that is oriented about orthogonal with respectto the surface 349. For purposes of this description, “about orthogonal”means within ±20 degrees of a normal to the surface 349.

8. COMPUTATIONAL HARDWARE OVERVIEW

FIG. 7 is a block diagram that illustrates a computer system 700 uponwhich an embodiment of the invention may be implemented. Computer system700 includes a communication mechanism such as a bus 710 for passinginformation between other internal and external components of thecomputer system 700. Information is represented as physical signals of ameasurable phenomenon, typically electric voltages, but including, inother embodiments, such phenomena as magnetic, electromagnetic,pressure, chemical, molecular atomic and quantum interactions. Forexample, north and south magnetic fields, or a zero and non-zeroelectric voltage, represent two states (0, 1) of a binary digit (bit).Other phenomena can represent digits of a higher base. A superpositionof multiple simultaneous quantum states before measurement represents aquantum bit (qubit). A sequence of one or more digits constitutesdigital data that is used to represent a number or code for a character.In some embodiments, information called analog data is represented by anear continuum of measurable values within a particular range. Computersystem 700, or a portion thereof, constitutes a means for performing oneor more steps of one or more methods described herein.

A sequence of binary digits constitutes digital data that is used torepresent a number or code for a character. A bus 710 includes manyparallel conductors of information so that information is transferredquickly among devices coupled to the bus 710. One or more processors 702for processing information are coupled with the bus 710. A processor 702performs a set of operations on information. The set of operationsinclude bringing information in from the bus 710 and placing informationon the bus 710. The set of operations also typically include comparingtwo or more units of information, shifting positions of units ofinformation, and combining two or more units of information, such as byaddition or multiplication. A sequence of operations to be executed bythe processor 702 constitutes computer instructions.

Computer system 700 also includes a memory 704 coupled to bus 710. Thememory 704, such as a random access memory (RAM) or other dynamicstorage device, stores information including computer instructions.Dynamic memory allows information stored therein to be changed by thecomputer system 700. RAM allows a unit of information stored at alocation called a memory address to be stored and retrievedindependently of information at neighboring addresses. The memory 704 isalso used by the processor 702 to store temporary values duringexecution of computer instructions. The computer system 700 alsoincludes a read only memory (ROM) 706 or other static storage devicecoupled to the bus 710 for storing static information, includinginstructions, that is not changed by the computer system 700. Alsocoupled to bus 710 is a non-volatile (persistent) storage device 708,such as a magnetic disk or optical disk, for storing information,including instructions, that persists even when the computer system 700is turned off or otherwise loses power.

Information, including instructions, is provided to the bus 710 for useby the processor from an external input device 712, such as a keyboardcontaining alphanumeric keys operated by a human user, or a sensor. Asensor detects conditions in its vicinity and transforms thosedetections into signals compatible with the signals used to representinformation in computer system 700. Other external devices coupled tobus 710, used primarily for interacting with humans, include a displaydevice 714, such as a cathode ray tube (CRT) or a liquid crystal display(LCD), for presenting images, and a pointing device 716, such as a mouseor a trackball or cursor direction keys, for controlling a position of asmall cursor image presented on the display 714 and issuing commandsassociated with graphical elements presented on the display 714.

In the illustrated embodiment, special purpose hardware, such as anapplication specific integrated circuit (IC) 720, is coupled to bus 710.The special purpose hardware is configured to perform operations notperformed by processor 702 quickly enough for special purposes. Examplesof application specific ICs include graphics accelerator cards forgenerating images for display 714, cryptographic boards for encryptingand decrypting messages sent over a network, speech recognition, andinterfaces to special external devices, such as robotic arms and medicalscanning equipment that repeatedly perform some complex sequence ofoperations that are more efficiently implemented in hardware.

Computer system 700 also includes one or more instances of acommunications interface 770 coupled to bus 710. Communication interface770 provides a two-way communication coupling to a variety of externaldevices that operate with their own processors, such as printers,scanners and external disks. In general the coupling is with a networklink 778 that is connected to a local network 780 to which a variety ofexternal devices with their own processors are connected. For example,communication interface 770 may be a parallel port or a serial port or auniversal serial bus (USB) port on a personal computer. In someembodiments, communications interface 770 is an integrated servicesdigital network (ISDN) card or a digital subscriber line (DSL) card or atelephone modem that provides an information communication connection toa corresponding type of telephone line. In some embodiments, acommunication interface 770 is a cable modem that converts signals onbus 710 into signals for a communication connection over a coaxial cableor into optical signals for a communication connection over a fiberoptic cable. As another example, communications interface 770 may be alocal area network (LAN) card to provide a data communication connectionto a compatible LAN, such as Ethernet. Wireless links may also beimplemented. Carrier waves, such as acoustic waves and electromagneticwaves, including radio, optical and infrared waves travel through spacewithout wires or cables. Signals include man-made variations inamplitude, frequency, phase, polarization or other physical propertiesof carrier waves. For wireless links, the communications interface 770sends and receives electrical, acoustic or electromagnetic signals,including infrared and optical signals, that carry information streams,such as digital data.

The term computer-readable medium is used herein to refer to any mediumthat participates in providing information to processor 702, includinginstructions for execution. Such a medium may take many forms,including, but not limited to, non-volatile media, volatile media andtransmission media. Non-volatile media include, for example, optical ormagnetic disks, such as storage device 708. Volatile media include, forexample, dynamic memory 704. Transmission media include, for example,coaxial cables, copper wire, fiber optic cables, and waves that travelthrough space without wires or cables, such as acoustic waves andelectromagnetic waves, including radio, optical and infrared waves. Theterm computer-readable storage medium is used herein to refer to anymedium that participates in providing information to processor 702,except for transmission media.

Common forms of computer-readable media include, for example, a floppydisk, a flexible disk, a hard disk, a magnetic tape, or any othermagnetic medium, a compact disk ROM (CD-ROM), a digital video disk (DVD)or any other optical medium, punch cards, paper tape, or any otherphysical medium with patterns of holes, a RAM, a programmable ROM(PROM), an erasable PROM (EPROM), a FLASH-EPROM, or any other memorychip or cartridge, a carrier wave, or any other medium from which acomputer can read. The term non-transitory computer-readable storagemedium is used herein to refer to any medium that participates inproviding information to processor 702, except for carrier waves andother signals.

Logic encoded in one or more tangible media includes one or both ofprocessor instructions on a computer-readable storage media and specialpurpose hardware, such as ASIC 720.

Network link 778 typically provides information communication throughone or more networks to other devices that use or process theinformation. For example, network link 778 may provide a connectionthrough local network 780 to a host computer 782 or to equipment 784operated by an Internet Service Provider (ISP). ISP equipment 784 inturn provides data communication services through the public, world-widepacket-switching communication network of networks now commonly referredto as the Internet 790. A computer called a server 792 connected to theInternet provides a service in response to information received over theInternet. For example, server 792 provides information representingvideo data for presentation at display 714.

The invention is related to the use of computer system 700 forimplementing the techniques described herein. According to oneembodiment of the invention, those techniques are performed by computersystem 700 in response to processor 702 executing one or more sequencesof one or more instructions contained in memory 704. Such instructions,also called software and program code, may be read into memory 704 fromanother computer-readable medium such as storage device 708. Executionof the sequences of instructions contained in memory 704 causesprocessor 702 to perform the method steps described herein. Inalternative embodiments, hardware, such as application specificintegrated circuit 720, may be used in place of or in combination withsoftware to implement the invention. Thus, embodiments of the inventionare not limited to any specific combination of hardware and software.

The signals transmitted over network link 778 and other networks throughcommunications interface 770, carry information to and from computersystem 700. Computer system 700 can send and receive information,including program code, through the networks 780, 790 among others,through network link 778 and communications interface 770. In an exampleusing the Internet 790, a server 792 transmits program code for aparticular application, requested by a message sent from computer 700,through Internet 790, ISP equipment 784, local network 780 andcommunications interface 770. The received code may be executed byprocessor 702 as it is received, or may be stored in storage device 708or other non-volatile storage for later execution, or both. In thismanner, computer system 700 may obtain application program code in theform of a signal on a carrier wave.

Various forms of computer readable media may be involved in carrying oneor more sequence of instructions or data or both to processor 702 forexecution. For example, instructions and data may initially be carriedon a magnetic disk of a remote computer such as host 782. The remotecomputer loads the instructions and data into its dynamic memory andsends the instructions and data over a telephone line using a modem. Amodem local to the computer system 700 receives the instructions anddata on a telephone line and uses an infra-red transmitter to convertthe instructions and data to a signal on an infra-red a carrier waveserving as the network link 778. An infrared detector serving ascommunications interface 770 receives the instructions and data carriedin the infrared signal and places information representing theinstructions and data onto bus 710. Bus 710 carries the information tomemory 704 from which processor 702 retrieves and executes theinstructions using some of the data sent with the instructions. Theinstructions and data received in memory 704 may optionally be stored onstorage device 708, either before or after execution by the processor702.

FIG. 8 illustrates a chip set 800 upon which an embodiment of theinvention may be implemented. Chip set 800 is programmed to perform oneor more steps of a method described herein and includes, for instance,the processor and memory components described with respect to FIG. 7incorporated in one or more physical packages (e.g., chips). By way ofexample, a physical package includes an arrangement of one or morematerials, components, and/or wires on a structural assembly (e.g., abaseboard) to provide one or more characteristics such as physicalstrength, conservation of size, and/or limitation of electricalinteraction. It is contemplated that in certain embodiments the chip setcan be implemented in a single chip. Chip set 800, or a portion thereof,constitutes a means for performing one or more steps of a methoddescribed herein.

In one embodiment, the chip set 800 includes a communication mechanismsuch as a bus 801 for passing information among the components of thechip set 800. A processor 803 has connectivity to the bus 801 to executeinstructions and process information stored in, for example, a memory805. The processor 803 may include one or more processing cores witheach core configured to perform independently. A multi-core processorenables multiprocessing within a single physical package. Examples of amulti-core processor include two, four, eight, or greater numbers ofprocessing cores. Alternatively or in addition, the processor 803 mayinclude one or more microprocessors configured in tandem via the bus 801to enable independent execution of instructions, pipelining, andmultithreading. The processor 803 may also be accompanied with one ormore specialized components to perform certain processing functions andtasks such as one or more digital signal processors (DSP) 807, or one ormore application-specific integrated circuits (ASIC) 809. A DSP 807typically is configured to process real-world signals (e.g., sound) inreal time independently of the processor 803. Similarly, an ASIC 809 canbe configured to performed specialized functions not easily performed bya general purposed processor. Other specialized components to aid inperforming the inventive functions described herein include one or morefield programmable gate arrays (FPGA) (not shown), one or morecontrollers (not shown), or one or more other special-purpose computerchips.

The processor 803 and accompanying components have connectivity to thememory 805 via the bus 801. The memory 805 includes both dynamic memory(e.g., RAM, magnetic disk, writable optical disk, etc.) and staticmemory (e.g., ROM, CD-ROM, etc.) for storing executable instructionsthat when executed perform one or more steps of a method describedherein. The memory 805 also stores the data associated with or generatedby the execution of one or more steps of the methods described herein.

9. ALTERATIONS, EXTENSIONS AND MODIFICATIONS

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. Throughout thisspecification and the claims, unless the context requires otherwise, theword “comprise” and its variations, such as “comprises” and“comprising,” will be understood to imply the inclusion of a stateditem, element or step or group of items, elements or steps but not theexclusion of any other item, element or step or group of items, elementsor steps. Furthermore, the indefinite article “a” or “an” is meant toindicate one or more of the item, element or step modified by thearticle.

What is claimed is:
 1. An autonomous vehicle, comprising: a lightdetection and ranging (LIDAR) system, comprising: a waveguide arraycomprising a plurality of waveguides, the waveguide array configured togenerate a plurality of beams in a first plane, each beam of theplurality of beams transmitted from a respective waveguide of thewaveguide array; a collimator configured to receive the plurality ofbeams from the waveguide array and output a plurality of collimatedbeams in the first plane, the plurality of collimated beams defining anangular spread; and a first scanner configured to adjust a direction ofthe plurality of collimated beams to be in a second plane from the firstplane, wherein the second plane is different than the first plane; asteering system; a braking system; and one or more processors configuredto: determine a range to an object based on a return signal receivedfrom reflection or scattering of the plurality of collimated beams bythe object; and control operation of at least one of the steering systemor the braking system based on the range.
 2. The autonomous vehicle ofclaim 1, further comprising a second scanner configured to adjust thedirection of the plurality of collimated beams to perform a sawtoothscan.
 3. The autonomous vehicle of claim 1, wherein the one or moreprocessors are configured to: identify a first angle and a second anglein the second plane; adjust, using the first scanner, a first componentof the direction of the plurality of collimated beams, wherein the firstcomponent is a first incremental angle in the first plane; adjust, usingthe first scanner, a second component of the direction of the pluralityof collimated beams, wherein the second component is a secondincremental angle in the second plane between the first angle and thesecond angle; and switch, for each first component and second component,between a first waveguide of the waveguide array to emit a transmit beamof the plurality of collimated beams and a second waveguide of thewaveguide array to receive a return beam corresponding to the returnsignal.
 4. The autonomous vehicle of claim 1, wherein the first scanneris a polygon scanner configured to rotate about an axis of rotation at aconstant speed.
 5. An autonomous vehicle control system, comprising: aLIDAR system comprising: a waveguide array configured to transmit aplurality of beams in a first plane; a collimator configured to receivethe plurality of beams from the plurality of waveguides and output aplurality of collimated beams in the first plane, the plurality ofcollimated beams defining an angular spread; and a first scannerconfigured to adjust a direction of the plurality of collimated beams tobe in a second plane from the first plane, the second plane differentthan the first plane; and a vehicle controller configured to controloperation of an autonomous vehicle using a range to an object determinedusing a return signal received from reflection or scattering of theplurality of collimated beams by the object.
 6. The autonomous vehiclecontrol system of claim 5, wherein the first scanner comprises at leastone of a reflective optic, a refractive optic, a galvanometer, amicroelectromechanical systems (MEMS) mirror, a voice coil actuatedmirror, or a polygon scanner.
 7. The autonomous vehicle control systemof claim 5, wherein the LIDAR system further comprises a second scannerconfigured to adjust the direction of the plurality of collimated beamsin to be in a third plane from the second plane.
 8. The autonomousvehicle control system of claim 5, wherein the second scanner isconfigured to adjust the direction of the plurality of collimated beamsto perform a sawtooth scan.
 9. The autonomous vehicle control system ofclaim 5, wherein the first scanner is a polygon scanner configured torotate about an axis of rotation at a constant speed.
 10. The autonomousvehicle control system of claim 5, wherein the waveguide array comprisesa plurality of waveguides and defines a first spacing of the pluralityof waveguides in a first region of the waveguide array and a secondspacing of the plurality of waveguides in a second region of thewaveguide array, wherein the first spacing is greater than the secondspacing.
 11. The autonomous vehicle control system of claim 5, whereinat least one of the scanner or a detector array is configured to receivethe return signal.
 12. A light detection and ranging (LIDAR) system,comprising: a waveguide array comprising a plurality of waveguides, thewaveguide array configured to generate a plurality of beams in a firstplane, each beam of the plurality of beams transmitted from a respectivewaveguide of the waveguide array; a collimator configured to receive theplurality of beams from the waveguide array and output a plurality ofcollimated beams in the first plane, the plurality of collimated beamsdefining an angular spread; and a first scanner configured to adjust adirection of the plurality of collimated beams to be in a second planefrom the first plane, wherein the second plane is different than thefirst plane.
 13. The LIDAR system of claim 12, wherein the collimator isconfigured to shape the plurality of beams into a fan of the pluralityof collimated beams.
 14. The LIDAR system of claim 12, wherein thecollimator is configured to define the angular spread for an object inan environment.
 15. The LIDAR system of claim 12, wherein the firstscanner is configured to rotate about an axis of rotation at a constantspeed.
 16. The LIDAR system of claim 12, wherein the first planeintersects the axis of rotation and the waveguide array is arrangedparallel to the axis of rotation.
 17. The LIDAR system of claim 12,wherein the waveguide array defines a first spacing of the plurality ofwaveguides in a first region of the waveguide array and a second spacingof the plurality of waveguides in a second region of the waveguidearray, wherein the first spacing is greater than the second spacing. 18.The LIDAR system of claim 12, wherein the first scanner is configured toperform a plurality of interleaved outputs by adjusting a direction ofthe plurality of collimated beams by an incremental angle between atleast a first interleaved output of the plurality of interleaved outputsand a second interleaved output of the plurality of interleaved outputs.19. The LIDAR system of claim 12, further comprising a second scannerconfigured to further adjust the direction of the plurality ofcollimated beams in the second plane such that the first scanner and thesecond scanner adjust the direction of the fan to be in a third planefrom the second plane to perform a step scan.
 20. The LIDAR system ofclaim 12, wherein the second scanner is configured to adjust thedirection of the plurality of collimated beams to perform a sawtoothscan.